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AUTOMOTIVE 
REFERENCE BOOK 


A complete reference book for 
the use of students of the Mich¬ 
igan State Auto School in con¬ 
junction with their courses in 
automotive construction, opera¬ 
tion, maintenance and repairing 



Published by 

Michigan State Auto School, Inc., 
Detroit, Michigan 



FIRST EDITION 

COPYRIGHT 1921 

By Michigan State Auto School, Inc. 













§)CI.A627579 

•4i 


NOV -4 1921 

'4 



/vvO I 


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< 3 ^ 


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ca 


PREFACE 


T his reference book is the result of ten years experi¬ 
ence in teaching and training men who desire to 
educate themselves thoroughly for positions in the 
automotive industries. The teaching of the subjects of 
our courses is highly specialized and requires a type of 
book, that, as far as we have been able to learn, has 
never been published. 

The fault of most text books lies in their being either 
too technical for the majority of students, or on the 
other hand incomplete, although claiming the virtue of 
simplicity. This reference book has been especially pre¬ 
pared by our staff for the benefit of the student receiving 
practical instruction in our school. It is intended for the 
beginner or the expert, but not for use as an engineer¬ 
ing text. 

No book of itself is sufficient to train a man in the 
automobile or allied industries. To gain the full benefit 
of such a book as this, it must be used in conjunction 
with the training and equipment provided in our class¬ 
rooms, laboratories and shops. 

The plan of our instruction is to alternate theory and 
practice. The material in the book has been classified 
under four headings—Engines, Chassis, Elements of 
Electricity and Advanced Electricity—^in order that the 
theory in each section may be completely explained and 
then followed by a period of actual shop practice. We 
have gone thoroughly into the various subjects treated 
but the simplicity of the text matter will be apparent to 
everyone. We are constantly adding equipment and im¬ 
proving our instruction in order to conform with the 
continuous developments in manufacturing and service. 

The drawings illustrating the text matter are repro¬ 
ductions of large charts especially prepared by our staff 
for use in our class work. 

Grateful acknowledgment is made-to the service man¬ 
agers, production managers and other executives of auto¬ 
mobile and tractor companies for their co-operation and 
appreciation of our efforts to establish and maintain the 
highest standards in the conduct of our school. 

MICHIGAN STATE AUTO SCHOOL, INC., 

By Arthur G. Zeller, 

October 1, 1921. Pres, and Gen. Manager. 





A LONGITUDINAL SECTIONAL VIEW OF A MODERN 

AUTOMOBILE 


























INTERNAL COMBUSTION 
ENGINES 


HISTORY 

The history of the Internal Combustion En¬ 
gine dates back some two hundred years, but 
it was not until 1826 that any progress was 
made and then only in an experimental way. 
At that time Brown invented what was known 
as the “Gas Vacuum Engine.” 

Brown’s engine was probably the first which 
did real work. It was clumsy and unwieldly, 
and soon had its place among the experiments 
and failures of that period. No approach to 
active explosive effect in a cylinder was reached 
until about 1838, and the years following im¬ 
mediately after. Barnett, in England, was the 
first to compress a mixture before exploding 
it. This was about 1860. Many patents 
were issued in Europe and in this country, but 
progress was spasmodic and its practical intro¬ 
duction for power purposes was slow. Subse¬ 
quent to 1860, practical improvements were 
produced in France, which were brought to the 
United States in 1862. This was followed by 
Beau de Rocha’s idea (the four stroke cycle 
principle) which he developed through a long 
series of experiments and trials. Later, two en¬ 
gineers named Otto and Langdon took up Beau 
de Rocha’s idea and developed the first practi¬ 
cal internal combustion engine. In 1870 im¬ 
provements were advancing at a steady rate, 
but largely in valve gear and precision of 
governing for variable loads. 

The early idea that slow combustion was 
necessary proved a detriment to advance¬ 
ment. A suggestion of Beau de Rocha’s in 
1862 dispelled these ideas and brought forth 
the truth. His experience taught that the 
rapidity of action in both combustion and ex¬ 
pansion was the basis of success in explosive 
engines. The application of the gasoline and 
oil engines to marine and automobile propul¬ 
sion had a most stimulating effect in develop¬ 
ing ways and means of applying it. The auto¬ 
mobile has been the main incentive in recent 
years. 

Kerosene oil engines have, however, been 
tardy in their development, due to the low 
volatility of the fuel, but are now being per¬ 
fected and will take a prominent place for a 
great many power purposes within the range 
of their application. 


DESCRIPTION AND FUNDAMENTAL 
PRINCIPLES 

The “internal combustion engine” is an en¬ 
gine in which heat energy is converted into 
mechanical energy, by the “combustion” of a 
gas or volatilized fluid directly in the engine. 
This is in contrast with the steam engine 
which may be- termed an “external combustion 
engine” since the heat energy of the fuel is 
transmitted to the water in the boiler and the 
water acts as a carrier, conveying the heat en¬ 
ergy to the engine where it is converted into 
mechanical energy. 

Combustion means the burning of a sub¬ 
stance, uniting with the oxygen of the air, 
forming gases. When this burning takes place 
with extreme rapidity and under the proper 
conditions an “explosion” occurs and a large 
amount of heat is generated. The effect of 
heat on gases in a closed receptacle is to make 
them expand, and it is the pressure and power 
due to this expansion that is utilized to oper¬ 
ate the internal combustion engine. By the 
combustion of the fuel directly in the engine, 
higher temperatures are obtained, resulting in 
a much greater efficiency. 

In the gasoline engine, the explosion is made 
to occur in a closed cylinder, and the expan¬ 
sion pressure utilized to move a plug or pis¬ 
ton, the motion of which is transmitted 
through the engine parts to the point where 
the power can be used. 

To make the movement of the piston con¬ 
tinuous requires the repeated production of 
explosions in the cylinder. This calls for sup¬ 
plying new charges of gas, providing the 
means for exploding them under proper condi¬ 
tions, and removing the burned gases. 

There are two principal systems for per¬ 
forming this series of operations in keeping 
a gas engine running. The systems, or series 
of operations, are called “cycles.” Engines are 
classified according to the number of strokes it 
takes to complete a cycle, and thus we have 
the “four stroke cycle engine” and “two stroke 
cycle engine.” 

The term cycle means a complete course or 
series of events beginning at any one point, 
continuing always in the same order and re¬ 
turning to the starting point. A cycle of oper¬ 
ations in the gas engine consists of supplying 


2 


ENGINES 



FIG. 2 

T-HEAD FOUR STROKE CYCLE ENGINE 





















































































































































































































































































FOUR STROKE CYCLE ENGINE 


3 


the fresh charge of gas, the compression, 
ignition and expansion of the charge, and ex¬ 
hausting of the burned gases. 

FOUR STROKE CYCLE ENGINE 

The parts involved in the construction of a 
four stroke cycle engine are: 

Cams 

Inlet Valve 
Exhaust Valve 
Valve Tappet 
Valve Spring 
Water Jacket 
Inlet Manifold 
Exhaust Manifold 
Flywheel 
Carburetor 
Spark Plug 

Functions of the Principal Parts 

The cylinder is a hollow stationary casting 
smoothly machined inside, in which the ex¬ 
plosion takes place. The piston is a carefully 
fitted movable plug which receives the force 
of the explosion. It moves back and forth in 
the cylinder, and this reciprocating motion is 
transmitted to the connecting rod, by means 
of which it is converted into a rotating motion 
through the means of a crankshaft. This 
shaft is connected to the transmission system 
to drive the car. 

The inlet valve controls the opening through 
which the fresh charge of gas is admitted to 
the cylinder. The exhaust valve controls the 


Cylinder 
Cylinder Head 
Piston 

Piston Rings 
Piston Pin 
Connecting Rod 
Crankshaft 
Main Bearings 
Crankcase 
Timing Gears 
Camshaft 


opening through which the burned gases leave 
the cylinder. Both valves are actuated by the 
valve tappets, these in turn being operated by 
cams on a camshaft which is driven from the 
crankshaft through the timing gears. The fly¬ 
wheel is a heavy balance wheel to keep the 
engine running between the power impulses. 
When the piston and crank are at the top ex¬ 
tremity of their travel the position is called the 
“top dead center” (T. D. C.) and when at the 
lower extremity of travel it is called the “bot¬ 
tom dead center” (B. D. C.). The distance 
the piston travels in the cylinder from one ex¬ 
tremity to the other is called the “stroke” of 
the engine and the movement causes the 
crankshaft to rotate one-half a revolution. 

“Four Stroke Cycle” can now be understood 
to mean that it requires four strokes of 
the piston or two revolutions of the crank¬ 
shaft (720 degrees circular travel) to complete 
the cycle of operations. 

The four strokes are called: 

1. Suction or Intake Stroke. 

2. Compression Stroke. 

3. Impulse or Power Stroke. 

4. Exhaust Stroke. 

Fig. 4 shows the positions of the principal 
parts of the engine in these four strokes. At 
(A) on the intake stroke, the piston is moving 
downward carried by the momentum of the fly¬ 
wheel or power applied to crankshaft; the ex¬ 
haust valve is closed and the inlet valve open. 
The downward movement of the piston causes 


FIG., 2 

T-HEAD FOUR STROKE CYCLE ENGINE 


1. Combustion chamber. 

2. Piston. 

3. Piston ring. 

4. Piston pin or wrist pin. 

5. Connecting rod. 

6. Connecting rod cap. 

7. Connecting rod bolts. 

8. Shims. 

9. Castle nuts. 

10. Oil dipper. 

11. Main bearing cap. 

12. Crankshaft. 

13. Crankshaft timing gear or 

master gear. 

14. Exhaust camshaft. 

15. Exhaust camshaft timing gear. 

16. Inlet camshaft. 

17. Inlet camshaft timing gear. 

18. Eccentric. 

19. Plunger. ] 

20. Plunger spring. | 

21. Housing. [ Oil pump. 

22. Check valves. 1 

23. Pet cock. J 

24. Inlet line. 

25. Outlet line. 

26. Crankcase. 

27. Oil pan. 


28. Oil trough. 

29. Oil level gauge. 

30. Oil filler and breather pipe. 

31. Screen. 

32. Oil pan drain plug. 

33. Pet cock. 

34. Port plug. 

35. Inlet valve. 

36. Inlet port. 

37. Inlet manifold. 

38. Exhaust valve. 

39. Exhaust port. 

40. Exhaust manifold. 

41. Valve stem guide. 

42. Valve spring. 

43. Valve spring retainer. 

44. Clearance. 

45. Clearance adjuster. 

46. Clearance adjuster lock nut. 

47. Tappet. 

48. Tappet guide'. 

49. Cylinder. 

50. Gasket. 

51. Radiator. 

52. Filler cap. 

53. Drain cock. 

54. Upper chamber. 

55. Lower chamber. 


56. Hose connection. 

57. Hose clamp. 

58. Water pump housing. 

59. Water pump drive gear. 

60. Water pump impellers. 

61. Water inlet to water jacket. 

62. Water outlet to water jacket. 

63. Water jacket. 

64. Valve cover or inspection plate. 

65. Wing or thumb nut. 

66. Fuel tank filler cap. 

67. Air vent. 

68. Fuel tank. 

69. Fuel inlet to carburetor. 

70. Main air inlet. 

71. Auxiliary air inlet, valve and 

spring. 

72. Float chamber. 

73. Mixing chamber. 

74. Float. 

75. Float needle valve. 

76. Fuel adjusting valve. 

77. Fuel jet. 

78. Spray nozzle. 

79. Venturi tube. 

80. Throttle or butterfiy valve. 

81. Spark plug. 



4 


ENGINES 


a vacuum in the cylinder, making the pressure 
lower than that of the atmosphere outside. The 
atmospheric pressure then forces air into the 
cylinder to replace the air displaced by the pis¬ 
ton and to balance the two pressures. As the 
air enters, it passes through the carburetor 
picking up some of the fuel, forming a vapor 
or gas, which is represented as entering 
through the inlet valve. 

At (B), just after the piston and crank have 
passed the bottom dead center the inlet valve 
closes, and the piston moving upward com¬ 
presses the charge of gas entrapped in the 
cylinder. The gas is compressed in order that 
it may be in a more compact mass when ig¬ 
nited, which condition aids in developing rapid 
and vigorous burning, producing great heat 
and consequent high pressure. It also con¬ 
fines the gas to a smaller space when the tem¬ 
perature is highest thus avoiding some loss by 


EXPANSION PRINCIPLE OF THE INTERNAL 
COMBUSTION ENGINE 

One of the scientific laws of gases states 
that the volume, pressure and temperature of 
any mass of gas are so closely related that no 
one of those properties can be changed without 
affecting one or both of the others. If the 
volume is kept constant, an increase in tem¬ 
perature will increase the pressure; a decrease 
in volume will increase temperature and pres¬ 
sure ; or an increase in pressure or temperature 
would tend to increase the volume. These facts 
are the basis upon which the internal combus¬ 
tion engine operates. 

During the compression stroke the charge of 
gas is decreased in volume and its temperature 
rises and the pressure increases. The instant 
the gas is ignited the temperature is again in¬ 
creased which tends to make the gas expand. 



FIG. 3 


CYCLE OF OPERATIONS 


This figure shows the approximate crankshaft posi¬ 
tions at the start and finish of each of the four strokes. 

The shading shows the length of the strokes with 
these valve openings and closings, the crankshaft turn¬ 
ing in a clockwise direction. . 


The position of the crankshaft at the start and finish 
of each stroke is represented by the lines at the end 
of the shading. 

The length of the stroke varies in different engines. 


radiation of the heat through the walls which 
hold it. 

Just before the piston reaches the top dead 
center the gas is ignited, usually by an electric 
spark. The heat due to the burning of the gas 
causes it to expand and develops a very high 
pressure which forces the piston down as 
shown at (C), imparting the impulse to the 
crankshaft. 

Before the piston reaches the bottom dead 
center again, the exhaust valve opens and the 
burned gases begin to escape, due to their be¬ 
ing at a higher pressure than the atmosphere. 
The upward movement of the piston shown at 
(D) caused by the momentum of the flywheel, 
aids in clearing the cylinder of the burned 
gases, until the exhaust valve closes as the 
piston passes the top dead center again, when 
the whole cycle of operation begins its repeti¬ 
tion. 


At that moment the gas, being confined in the 
cylinder, is prevented from expanding so the 
pressure begins to increase until it is sufficient 
to move the piston. 

This can be demonstrated by taking a metal¬ 
lic can, sealing up its opening and then heating 
it to raise the temperature a considerable 
amount. The can will begin to bulge due to 
the fact that the air or gas inside is expanding 
from the increase in temperature. If the tem¬ 
perature is still further increased the can will 
burst because, the walls of the can having 
limited the amount of expansion, the pressure 
will increase until it reaches an amount greater 
than the construction of the can will with¬ 
stand. 

All substances do not have the same com¬ 
bustion properties. Some burn quickly and 
some very slowly. Powder, for instance, burns 
with extreme rapidity, while kerosene or gaso- 










FOUR STROKE CYCLE ENGINE 


5 




ENGINE OPERATIONS 


These illustrations show the relative positions of the crankshaft, piston, cams, and 

valves as the various strokes begin. 


























































































































































































6 


ENGINES 





Fig. 5 

T-HEAD FOUR STROKE CYCLE ENGINE 


This figure 


shows the complete assembly of a single cylinder T-head engine, with its accessories. 


























































































































































































































































PRINCIPLES AND THERMAL EFFICIENCY 


7 


line burn slower. This difference in the rate of 
combustion has much to do with the power 
available. The quick burning substances or 
fuels indicate a rapid temperature rise and 
quick expansion; the less inflammable fuels, 
burning more slowly, require more time for 
transmitting the power of the expanding gas. 

In present practice the fuel charge is com¬ 
pressed to between 70 and 80 pounds gauge 
pressure. The higher the compression the 
greater the power obtained and the higher the 
fuel economy, but when the compression ex¬ 
ceeds a certain limit there is danger of trou¬ 
ble from overheating of the cylinder and from 
“self-ignition” or “pre-ignition” due to the 
heat generated by compression. 

The following figures show what tempera¬ 
ture the gases reach under the influence of 
compression pressures, the temperature before 
compressing being 60 degrees Fahrenheit in 
each case: 

Compression to Temperature 

attained. 

30 lbs. (gauge).258 degrees F. 

60 lbs.373 degrees F. 

90 lbs.490 degrees F. 

This shows that an increase in compression 
will cause an increase in the temperature of 
the gases without the application of any other 
heat. If the normal operating temperature of 
the engine is added to this, it would be possible 
to raise the temperature of the gases to a 
very high point, sufficient to pre-ignite them. 

The temperature of combustion is approx¬ 
imately 2500 degrees to 3000 degrees Fahren¬ 
heit. These temperatures are considerably be¬ 
low the theoretical temperature of combus¬ 
tions, but many conditions are present to cause 
this difference. If such a high temperature 
was allowed to continue, the metal parts of the 
engine would bind or “seize,” since metals ex¬ 
pand in the same manner as gases when heat 
is applied, except that the amount of expansion 
is less and it varies in different metals. 

To prevent the engine from attaining this 
excessive temperature, a circulation of air or 
water around the cylinder is provided to carry 
away a portion of the heat. Here then are two 
agencies apparently working against each 
other both of which are necessary. The higher 
the combustion temperature of the fuel, the 
more power available. Hence it is the prob¬ 
lem of the automobile engineer to design the 
engine in such a manner as to dissipate the 
excessive heat sufficient to protect the mater¬ 
ials used and yet allow the fullest value to be 
extracted from the fuel. 

This problem involves the size and shape of 


the combustion chamber,—the portion of the 
cylinder in which the gas is exploded,—as well 
as the type of cooling system. The most com¬ 
mon cooling method used is water-cooling; a 
jacket is provided to allow the water to cir¬ 
culate around the cylinder where it is exposed 
to the high temperature. Great care must be 
used to see that the cooling system is always 
filled with water. In any cooling system how¬ 
ever, much of the heat value of the fuel is car¬ 
ried away without its rendering any useful 
work, which reduces materially the power de¬ 
livered by the engine. 

In the lower portion of the crankcase there 
is provided a sump or reservoir containing lu¬ 
bricating oil. As the crankshaft rotates, a 
spoon or dipper on the connecting rod comes 
in contact with the oil. As it travels upward 
it throws or splashes oil into the engine, lubri¬ 
cating the cylinder wall, piston, piston rings, 
piston pin and bearings. All moving surfaces 
in the interior of the engine are lubricated 
from this source. 

THERMAL EFFICIENCY 

In addition to the loss of heat through the 
cooling system, other conditions, some of them 
peculiar to the gas engine, combine to reduce 
the efficiency of its operation. The internal 
friction of the engine itself consumes a certain 
amount of power; the low grade of fuel com¬ 
bined with inlet manifold design, and the im¬ 
possibility of designing a carburetor suitable 
for all load and speed conditions causes some 
fuel to enter the cylinder in liquid form, un¬ 
vaporized; also the exhaust gases leave the 
cylinder before all of the available heat energy 
has been given up. 

The efficiency of an engine is determined by 
comparing the amount of energy put into it 
with the amount of energy it delivers in the 
form of work. The ratio between the number 
of heat units supplied in the fuel and the use¬ 
ful work actually performed expressed in heat 
units, is called the “Thermal Efficiency.” The 
gas engine is the most efficient type of heat 
engine. In some designs the efficiency is as 
high as 35%, while in the average automobile 
engine it is approximately 17% to 20%. The 
losses vary in different engines, but they may 
be divided approximately as follows, using the 
total amount of fuel supplied as 100%: 


Friction . 13% 

Exhaust. 30% 

Cooling . 40% 

Power available. 17% 


Total .100% 












8 


ENGINES 


DEFINITIONS 

INTERNAL COMBUSTION ENGINE TERMS . 

Bore is the internal finished diameter of the 
cylinder. 

Stroke is the distance moved by the piston 
from one extreme end of its travel to the 
other, or from top dead center to bottom 
dead center positions. The stroke is al¬ 
ways twice the radial distance from the 
center of the crankshaft to the center of 
the crank pin. 


Combustion Chamber is the name given to the 
space in which the gaseous fuel is ignited 
and exploded. It includes all the clear¬ 
ance space above the piston when it is on 
top dead center. 

Linear Velocity is the combination of units of 
distance and units of time. It is the rate 
of motion and is expressed in “feet per 
minute” or “feet per second.” 


Velocity 


Distance 

Time 



INDICATOR CARD, INTERNAL COMBUSTION ENGINE 


An indicator card showing the mean effective pres¬ 
sure readings of a typical engine. 

1. Inlet valve opening. 

2. Inlet valve closing. 

3. Exhaust valve opening. 

4. Exhaust valve closing. 

5. Ignition. 


The average temperature at end of the intake stroke 
is about 260° F. and at the end of the compression 
stroke is about 850° F. 

The temperature during the power stroke rises to as 
high as 3000° F. and at the start of the exhaust stroke 
the temperature is about 1000° F. At the end of the 
exhaust stroke the temperature is about 300° F. 


Displacement is the volume displaced by the 
piston in moving the length of the stroke. 
To calculate the displacement, multiply 
the cross sectional area of the cylinder in 
square inches by the stroke in inches, as 
expressed in formula. Displacement (cubic 
inches) = area X stroke. 

For example, the displacement of an en¬ 
gine with 4 inch bore and 5 inch stroke 
would be; 

Area=D^X.7854=4X4X.7854=12.566 sq. in. 

Stroke=5 in. 

12.566 X 5 = 62.83 cubic inches. Ans. 

Volumetric Clearance is all the space above the 
piston when it is on top dead center, in¬ 
cluding valve pockets, etc., and is ex¬ 
pressed in terms of displacement. The 
clearance percentage equals the clearance 
volume divided by the displacement. 


Circular or Angular Velocity is given in revo¬ 
lutions per minute (R. P. M.) or degrees 
per minute. 

Piston Speed is the summation of the distances 
traversed by the piston in its up and down 
movement in a certain period of time. It 
is the velocity at which the piston is mov¬ 
ing. Thus, in an engine with 5 inch stroke 
making 600 R. P. M. or 1200 strokes per 
minute the piston speed would be 
1 900 N/ 

~ ^ ^ = 500 ft. per minute. 

xZ 

Pressure expresses the force acting upon a cer¬ 
tain area. It is usually calculated as act¬ 
ing upon a unit area and expressed in 
“pounds per square inch.” 

Work is the combination of the units of weight 
or force and distance. It is the overcom¬ 
ing of resistance (usually measured in 
pounds) through a certain distance. It is 


% 
































DEFINITIONS 


9 


calculated by multiplying the moving 
force, in pounds, by the distance moved, 
in feet. 

The unit of work is the amount of work 
done by a force of one pound moving 
through a distance of one foot and is 
called the “foot-pound.” 

Power is the rate at which work is done. The 
most common unit of power is the horse¬ 
power (H. P.) and was established by 
James Watt as the power of a strong 
draft horse and used by him to measure 
the power of steam engines. Power 
equals work (in foot pounds) divided by 
the time. One H. P. equals 33,000 foot 
pounds per minute. 

The indicated horse-power (I. H. P.) is 
the horse-power actually developed with¬ 
in the cylinder, and may be calculated 
from an indicator card, the engine dimen¬ 
sions and the speed of the engine at the 
time the indicator card was taken. The 
mean effective pressure (M. E. P.) is de¬ 
termined from the indicator card and rep¬ 
resents the average of the pressures at the 
different positions of the piston. 


inch bore and 5 inch stroke. Indicator 
card shows M. E. P. = 90 lbs. per sq. in.; 
engine running 2000 R. P. M. Then 


P = 90 
L = 5/12 

A = 42 X .7854 = 12.566 


N = 2000 

= 57.12 Ans. 

ooUU V 


In practical work the brake horse-power 
(B. H. P.) rate is used instead of the I. H. 
P. The B. H. P. is obtained by a dynamo¬ 
meter test or Prony Brake test. The B. 
H. P. is the horse-power that is delivered 
by the crankshaft for useful work. 

By substituting certain assumed values 
in the above formula, the automobile en¬ 
gineers have developed a shorter formula 
which is generally accepted in the ap¬ 
proximate rating of automobile engines. 
The formula was formerly known as the 
A. L. A. M. (American Licensed Automo¬ 
bile Manufacturers) formula, but has 
been adopted by the National Automobile 



POUNDS COMPRESSION. 

FIG. 7. 



FIG 8. 


COMPRESSION CHART 


POWER CHART 


This chart shows that as the compression is raised This chart shows that as the engine speed is in- 
the power developed increases until the point of pre- creased the power developed is also increased, until 
ignition is reached. the maximum power is developed. 


The horse-power formula is; 


I. H. P. 


PLANX 

33000 


in which P = M. E. P. 

L = Length of stroke in feet. 

A = Area of piston in sq. in. 

N = R. P. M. 

X = Number of impulses per 
revolution. 

For example :-Calculate the I. H. P. of a 
4 cylinder, 4 stroke cycle engine with 4 


Chamber of Commerce, The Society of 
Automotive Engineers and the Royal Auto¬ 
mobile Club of Great Britain. This form¬ 
ula is based on an M. E. P. of 90 lbs. per 
sq. in., any combination of stroke and 
R. P. M. that gives a piston speed 
of 1000 feet per minute, and is written 
D2 X N 
2.5 

in which D = the’ diameter of the cylin¬ 
der in inches and N = the number of 










































10 


ENGINES 


cylinders. Using the same example as be¬ 
fore, a 4 cylinder, 4 stroke cycle engine 
with 4 inch bore, 

D = 4 
N = 4 

Then H. R = ^~^ =25.6 Ans. 

This would be the approximate horse¬ 
power developed by that engine when run¬ 
ning at 1200 R. P. M., the engine speed 
which would give a piston speed of 1000 
feet per minute. This same engine would 
probably develop a much higher horse¬ 
power at its maximum speed, for the 
horse-power increases as the engine speed 
increases until the maximum power point 
is passed. 

Torque is a twisting or turning force. When 
used in reference to the engine it is the 
effort or pull in pounds exerted by the 
crankshaft at a certain radius. In a 
sense, it is independent of the power of the 
engine, for the torque may be low and 
yet if the engine speed is high the horse¬ 
power will be high. The Prony Brake test 
is determining the horse-power by measur¬ 
ing the torque. 

Density is the comparison of weight and vol¬ 
ume. It is the weight per unit of volume. 

Specific Gravity is the comparison of the den¬ 
sity of a substance with the density of 
water, or the weight of the substance com¬ 
pared with the weight of an equal volume 
of pure water at a temperature of 39.2 
degrees F. The specific gravity of gases 
is determined by comparing their weights 
with the weight of air. 

Specific Heat is the ratio between the heat re¬ 
quired to raise the temperature of a cer¬ 
tain weight of any substance one degree, 
and the heat required to raise the same 
weight of water from 62 degrees to 63 de¬ 
grees F. 

Calorific Value is the amount of heat given up 
by a unit quantity of any fuel that is 
burned under proper conditions. It varies 
in different fuels. A good general figure 
to use for the average gasoline of today is 
20,000 B. T. U. (British Thermal Units) 
per pound. 

The B. T. U. is the unit of heat, and is 
the amount required to raise the temper¬ 
ature of one pound of pure water from 62 
degrees to 63 degrees F. 

The Mechanical Equivalent of heat is 
the amount of mechanical energy equiva¬ 
lent to the heat energy in one B. T. U. 
Heat and energy being mutually converti¬ 


ble, one B. T. U. = 778 foot-pounds. 
Since one H. P. -- 33,000 foot-pounds per 
minute, one H. P. = 2545 B. T. U. per 
hour. 

Scavenging is the process of clearing the cyl¬ 
inder of the burned gases. 

Flame Propogation is the rapidity of combus¬ 
tion or spreading of the flame through the 
gaseous mixture after it has been ignited. 
It is affected both by the quality of the 
mixture and the compression pressure. 
For certain compression pressures and 
certain fuels there is one proportion of 
mixture at which the flame spreads the 
fastest. Even a slight deviation from that 
proportion will make a marked difference 
in the velocity of propogation, the power, 
and the thermal efficiency of the engine. 
Weak compression or an excess of air or 
of gas will retard the velocity of the flame 
spreading and require the spark to be ad¬ 
vanced to obtain proper results. 

Pre-ignition is the premature explosion of the 
gas in the cylinder. It may be' caused by 
too high compression, ignition spark too 
early, or carbon deposit in the cylinder. 

CYLINDERS 

Types 

There are four types of cylinder construc¬ 
tion, named from the form in which the cast¬ 
ing is made,—T-head, L-head, I-head, F-head. 

In the T-head type the inlet and exhaust 
valves are placed on opposite sides of the 
cylinder, making a large combustion chamber, 
projecting both sides of the cylinder. This 
results in an excessive amount of surface being 
exposed to the cooling medium, and causes a 
loss of power in the fuel mixture, also using a 
greater amount of fuel than other types of 
cylinders to develop a given horse-power. This 
type is but little used, only 21 / 2 % of passenger 
car engines and 4i/^% of truck engines being 
T-head. 

In the L-head type, both valves are on the 
same side of the cylinder, thus reducing the 
size of the combustion chamber about one half. 
Although not the best, this arrangement is a 
decided advantage over the T-head from a 
standpoint of thermal efficiency, for the reason 
that it has a smaller amount of surface ex¬ 
posed to the cooling medium. It also has the 
mechanical advantage of requiring but one 
camshaft, instead of two as on the T-head. 
All the cams are placed on the one shaft and 
driven by one set of gears. About 66% of the 
engines used in passenger cars and 87% of 
those used in trucks today are of L-head type. 

The valve-in-head or I-type gives the high¬ 
est thermal efficiency, because of small com- 





CYLINDERS 


11 


bustioii chamber, all of it directly over piston 
head. The elimination of the side pockets of 
the L and T-head type has removed the dead 
spaces where ineffective gases may remain. 
The valve arrangements are about equally 
divided between inclined valves and straight or 
perpendicular valves. The valves are actuated 
by rocker arms which receive their motion 
through push rods from a camshaft located as 
in the other type, or by an overhead camshaft 
driven from the crankshaft through a series 
of bevel gears. About 24% of passenger car 
engines are of this type. 

The F-head cylinder is a compromise, to ob¬ 
tain some of the advantages of the T and L- 
head. The inlet valve is placed in the head and 
the exhaust valve at the side. This results in 
better scavenging of the cylinder, reduces the 
size of the combustion chamber to approxi¬ 
mately that of the L-head cylinder and yet 


allows large valves to be used as in the T-head 
cylinder. The thermal efficiency is no better 
than that of the L-head. 

Material and Construction. 

The most common material used in cylinder 
construction is cast iron with a heavy con¬ 
tent of graphite, making it a very good wear 
resisting material. Graphite has a tendency 
to lubricate, which reduces the percentage of 
wear at a high temperature. Some cylinder 
blocks are constructed of aluminum with steel 
or cast iron sleeves pressed or threaded into 
the aluminum block. Others are constructed 
of steel, such as the aircraft engine where 
the cylinders are machined both on the inside 
and outside and the water jacket is brazed or 
welded to the cylinder. The reason for this 
is that in a casting the cylinder walls and other 
parts may not be of the same uniform cross 
section. If not the same, when the tempera- 



- FIG. 9 

TYPES OF CYLINDER AND VALVE ARRANGEMENTS 


This figure shows some of the various shapes of 
combustion chambers and arrangements of valves. 
Illustration (A) represents the I-head cylinder having 
both valves in the head of the cylinder over the piston, 
being operated by one camshaft. 

Illustration (B) represents the T-head cylinder, hav¬ 
ing the inlet and exhaust valves on opposite sides of the 


combustion chamber, being operated by two camshafts. 

Illustration (C) represents the L-head cylinder, hav¬ 
ing the inlet and exhaust valves on the same side, being 
operated by one camshaft. 

Illustration (D) represents the F-head cylinder, hav¬ 
ing one valve mounted at the side and one in the head, 
both operated by one camshaft. 











































































































12 


ENGINES 


ture rises the expansion will not be the same 
in all parts of the cylinder, causing the cylin¬ 
ders to warp. The cylinders of the aircraft 
engine, in order to minimize this unequal 
expansion, are machined on the inside and out¬ 
side. Steel cylinders are not used to any ex¬ 
tent in automotive construction, since they are 
more expensive and less serviceable. Cast iron 
is used almost entirely. 

Cylinder heads are usually constructed of 
cast iron and are as a rule cast with the 
water jacket incorporated in the head itself. 
This is done by placing cores inside of the 
mould before the cylinder head is cast. 

The cylinder head joint is made air tight 
by the use of a gasket. This gasket con¬ 
sists of two layers of thin sheet copper which 
cover a sheet of asbestos. The head is held 
down by bolts or studs. These bolts are not 
plain cold rolled steel, but are, as a rule, heat- 
treated alloy steel. Where the head is not re¬ 
movable, an arrangement of port plugs is pro¬ 
vided for easy access to the valves. The 
port plugs are screwed into threaded holes on 
the top of the engine, generally directly above 
the valves. The port plugs are set on a gas¬ 
ket in order that an air tight connection may 
be made. In some cases, the port plugs are 
held down by clamps. The same type gasket 
is used for the port plug as under the cylinder 
head. Cover the port plug threads with graph¬ 
ite and grease so that they will be air tight 
when screwed down and can be easily removed. 

Finishing 

The cylinder walls are finished in several 
ways. The block is first cast in sand molds 
made from a pattern, then placed on a boring 
machine and the cylinder is bored out to the 
required size, perfectly round and straight. 
The various methods of finishing the barrel 
or bore are for the purpose of obtaining as 
smooth a surface as possible thereby reducing 
the development of friction. 

After the boring, two processes are used to 
finish the inner surface to accurate size and 
leave a very smooth surface. The first is 
reaming. The cylinder is bored to a diameter 
a fraction of an inch smaller than required, 
and then the reamer, a fiuted boring tool 
ground accurately to size, is run through leav¬ 
ing a smooth surface of correct dimensions. 

The other process is grinding. This is by 
far the best method of finishing the interior 
wall, for the reason that it is done with high 
speed wheels and the rough effect is not left 
in the barrel as it is with the slower operating 
tools. The grinding wheels are not affected 
by the hard spots in the metal as are the cut¬ 
ting tools, therefore a uniform job is insured 
when finished. 


Troubles and Repairs 

The more common interior cylinder troubles 
are cylinder scores or cylinder warped and out 
of round. These troubles are all corrected by 
one of the following processes: Boring, grind¬ 
ing, reaming or lapping. The lapping, how¬ 
ever, cannot be used to correct scored and 
warped cylinders without first boring, grinding 
or reaming. Tools must be used to straighten 
up the job and then merely smoothen by lap¬ 
ping. These repairs invariably necessitate new 
pistons and rings, as the size of the cylinder 
barrel is enlarged considerably. 

For lapping, use an old piston with the rings 
removed, and with a grinding compound on 
the surface of the piston, place it in the cylin¬ 
der, then force the piston up and down in a 
reciprocating and rotary movement, using a 
stroke the full length of the cylinder wall. 
After the cylinder wall is polished down 
smooth, take the new oversize piston, the head 
of which can just be started in the bottom of 
the cylinder, apply the grinding compound, 
and by turning it back and forth, gradually 
work the piston through. Then remove the 
piston and the lapping compound and measure 
the clearance. If the clearance is not suffi¬ 
cient, replace compound and proceed as form¬ 
erly, using full length strokes until sufficient 
clearance is obtained, and then the rings may 
be fitted. 

The more common outside troubles to 
cylinder blocks are cracked water jackets. 
The jackets are, as a rule, cast in one piece 
with the cylinder blocks. The most common 
method of repairing is the salting, rusting, or 
crystalizing process. 

If the crack is not very large and has not 
been cracked too long, it may be repaired by 
placing a 20% solution of Copper Sulphate 
(Blue Vitriol) in a squirt can, and squirt it 
into the crack. This will cause crystals to 
form within the crack. 

Dissolve about one pound of chloride of 
sodium, or common table salt, in about three 
gallons of water. Pour this in the water outlet 
at the top of cylinder, after stopping up the 
water inlet at the bottom. Allow the solution 
to stand above the level of the crack until the 
leak stops. This solution will only affect the 
freshly exposed metal in the crack, causing 
rust. 

Dissolve one pound of sal ammoniac crystals 
in five gallons of water and pour this into the 
water jacket the same as in the above case. 
This will also cause rust to form in the crack 
stopping the leak. 

Any of the above solutions will soon rust 
the crack so that the jacket will hold water, 
until such a time as the engine is run with¬ 
out water or allowed to become heated above 



CYLINDERS 


13 


the normal operating temperature. This may 
be caused by lack of cooling water or lubrica¬ 
tion. Where the crack is large or old, these 
solutions will be ineffective. To repair, clean 
off the surface about one inch on each side 
of the crack. With a small sharp cold chisel 
cut a small “V” shaped trench along with the 
crack. Rub the surface well with a piece of 
copper, and then clean the surface well with 
raw muriatic acid, apply soldering salts and 
tin the surface, and then apply hard solder 
until the crack is well filled. Dress down 
smooth and paint. 

Where the crack is large and hard to 
solder, it may be repaired by drilling a row of 
small holes about one-half inch apart in the 
crack. Use a blow torch to heat the metal 
around the crack and small holes. Take ordin¬ 
ary copper rivets and drive them into the holes 
in the crack while hot. The cylinder jackets 
when cooling contract so that the rivets will 
be held firmly in place. Now take a cape chisel 
or narrow cold chisel a‘nd groove the crack 
about 1/16" deep. Clean thoroughly with raw 
muriatic acid or any other cleaning acid that 
will penetrate to all parts where the solder 
should reach. Heat with blow torch and then 
apply hard solder in such quantity as to form a 
mound over the crack. Dress the surface with 
a file or with a grindstone and paint to cover 
all traces of the work. 

Probably the best method, although the least 
desirable for the repairing of water jackets, is 
welding or brazing. It may result in warping 
and cracking. Unless properly pre-heated this 
invariably necessitates reboring of the barrel 
if an accurate job is desired. Due to the fact 
that the cross sectional area of the cylinder 
walls is not the same all the way through, the 
expansion will be greater at some points, and 
less at others, causing the cylinder walls to 
become out of round or to warp. This will 
require reboring in order that the engine will 
have a true cylinder barrel. 

Carbon Deposit 

The formation of carbon in the combustion 
chamber is one of the causes of engine knock¬ 
ing. The deposit of carbon may be caused by 
(1) an excessive amount of lubricating oil get¬ 
ting into the combustion chamber; (2) by 
using low grade fuel, or (3) too rich a mixture. 

In the first cause, the lubricating oil works 
up by the piston, and since it contains some 
of the same elements as are in the fuel, 
the excessive heat tends to break it up or 
destroy it, the lighter parts passing off as a 
vapor, leaving the carbon to cook or bake on 
to the surfaces of the combustion chamber. 
With the other two causes, incomplete com¬ 
bustion leaves a certain amount of carbon from 
the fuel in the cylinders, which hardens or 


cakes on to the surfaces from exposure to the 
high temperatures. 

The combustion chamber should be finished 
as smooth as possible as there is less tendency 
for carbon to adhere to a smooth surface. The 
deposits of carbon reduce the size of the com¬ 
bustion chamber, causing a higher compres¬ 
sion pressure and a corresponding increase in 
temperature. Carbon also holds the heat, pre¬ 
venting it from radiating properly to the cool¬ 
ing medium. These conditions may result in 
a temperature sufficiently high to cause pre¬ 
mature ignition of the gas. Carbon deposit 
will also cause the spark plugs to become 
fouled, resulting in a failure of the plug to 
deliver the necessary spark for igniting the 
charge of fuel. 

Carbon may be removed by several dif¬ 
ferent methods. It may be partly removed 
by adding water to the mixture, a little at a 
time, when the engine is hot and running at 
high speed. This water must be introduced 
slowly and above the spray nozzle in the car¬ 
buretor, otherwise the engine will stop. 

Another method is to remove the spark plugs 
or open the petcocks and with a squirt can 
place a few spoonfuls of kerosene into each 
cylinder. Then with the ignition off, spin the 
engine over fast, allowing this kerosene to be 
thrown around, saturating the entire surface 
of the combustion chamber. Allow the kero¬ 
sene to remain in the cylinder over night. The 
next morning when the engine is started the 
carbon that is dissolved will pass out with the 
exhaust gases. 

After this deposit remains in the combustion 
chamber for some time it will form in such a 
hard scale that the above methods may not be 
effective. If that is the case, remove the port 
plugs or cylinder head and scrape this deposit 
out. At the same time it is usually necessary 
to grind the valves. Carbon may also be 
removed by burning it out with an oxygen 
torch, but care must be taken not to overheat 
or cause the piston or cylinder to become out 
of round from unequal expansion. Scraping 
the carbon is preferable. 

If the combustion chamber is too small, 
there may be premature explosions when the 
engine is running slowly on a hard pull. The 
mixture is ignited from the high tempera¬ 
ture that is caused by the increased compres ¬ 
sion. This is termed a compression knock 
and may be overcome by replacing the cylin¬ 
der head gasket with a thicker one or by plac¬ 
ing a fiber gasket underneath the cylinder, 
if the cylinder is removable from the crank¬ 
case. 

Having the spark advanced too much will 
also cause ignition of the gases before the 
piston reaches top dead center, resulting in a 
knock termed, spark knock. 




14 


ENGINES 


PISTONS 

The piston serves a triple function. It forms 
the movable wall of the combustion chamber, 
allowing its volume to be increased or de¬ 
creased. It receives the force of the explosion 
pressure and transmits that pressure to the 
connecting rod and also acts as a crosshead, 
transmitting the angular thrust of the con¬ 
necting rod to the cylinder wall. 

Since the pressure in the combustion cham¬ 
ber is sometimes as high as 400 lbs. per square 
inch, it is necessary to provide some means of 
making the piston gas tight. The piston head 
heats more than the cylinder wall, because it 
is not cooled by the water jacket; the head end 
of the piston heats more than the open end 
because it is exposed to the heat of the burning 
gases. These facts, and the difference in ex¬ 
pansion due to these varying temperatures, 
make it impossible to finish the piston itself 
tight enough to form the proper seal. This is 
accomplished by using flexible split metallic 
rings, called piston rings, three or four of them 
being placed in grooves turned on the outer 
circumference of the piston to receive them. 
These rings expand and contract with the 
changes in temperature, are made so as to 
exert a pressure against the cylinder wall over 
their entire surface, and with the aid of the 
lubricating oil, they maintain practically an 
airtight seal between the combustion chamber 
and the crankcase. This is termed the “com¬ 
pression seal” and its purpose is to keep the 
fuel mixture in the combustion chamber dur¬ 
ing compression and after its ignition. 

The shape of the piston head has consider¬ 
able effect upon the thermal efficiency of the 
engine. The ideal form would be a concave 
head, as this would concentrate the heat of 
combustion in the center of the combustion 
chamber, away from the cylinder walls, where 
it would be radiated to the water jacket. How¬ 
ever, this shape is of weak construction and 
also gathers carbon readily, so is not used. In 
present practice the heads are fiat or convex 
and finished smooth. 

To provide for the uneven expansion of the 
piston and the cylinder walls and to allow for 
lubrication, a certain amount of clearance is 
allowed between the two. The cylinder is 
bored to exact even dimensions and the piston 
finished a certain amount smaller. The aver¬ 
age practice is to allow .002" to .003" per inch 
of diameter at the piston head, and .001" to 
.0015" per inch of diameter at the open end. 
This clearance varies with different metals 
used and also on different designs of engines 
and the purposes for which they are to be used. 

There are usually three piston rings used 
above the piston pin and perhaps one below. 


The lower ring acts more as an oil carrier. 
The grooves are finished about .0005" wider 
than the ring and are deep enough to insure 
the ring not touching the bottom of the groove 
at any point after the piston and ring have 
been inserted in the cylinder. 

There is sometimes an oil groove below the 
bottom ring with holes drilled through the pis¬ 
ton wall, so that as the piston moves down¬ 
ward the ring will act as a scraper, scraping 
the oil into the groove, where it will flow 
through the holes and drop back into the 
crankcase. The grooves act as oil carriers to 
keep a film of oil on the cylinder walls both 
for lubrication and to form a seal between the 
piston ring and cylinder wall. 

In multiple cylinder engines all the pistons 
should be of exactly the same weight. If one 
piston is heavier or lighter than the others it 
causes an unbalanced condition which results 
in an excessive vibration and unnecessary wear 
on the bearings. 

The piston pin which forms the connection 
between the piston and the connecting rod is 
carried in bearings in the walls of the piston. 
These bearings are provided with bronze bush¬ 
ings which are pressed into place if the piston 
pin is designed to move in them. In some 
pistons the pin is made fast in the bearings 
and the connecting rod moves on the pin, 
in which case there are no bushings in the 
bearings in the piston. 

The distance from the top of the piston to 
the center of the piston pin should be the same 
on all pistons in an engine. Should these dis¬ 
tances vary, the compression would be unequal 
and cause vibration. 

Material 

The piston is usually made of cast iron, the 
grade of material being somewhat softer than 
used in the cylinder, so that the wear will come 
upon the piston, which is easier and cheaper 
to replace. Much experimenting is now being 
done with an aluminum alloy, the advantage 
being its light weight, which is of considerable 
value in eliminating vibration. In the recipro¬ 
cating motion of the piston its weight has to 
be started and stopped twice in every revolu¬ 
tion. Power is used in starting this weight, 
but of more importance is the vibration caused 
by overcoming the energy stored up in the 
moving parts after they are in motion. The 
aluminum piston has another advantage in the 
fact that carbon will not adhere to it as readily. 
It also radiates heat much more rapidly than 
cast iron and will therefore be cooler than the 
iron piston, a condition which permits higher 
compression pressures. Aluminum expands 
more than cast iron when heated so that a 



PI S T O N —PI S T O N RINGS 


15 


larger clearance is necessary, the usual prac¬ 
tice being to allow about twice the amount 
used on cast iron pistons. The aluminum 
piston may have a tendency to slap and knock 
when cold on account of this extra clearance, 
but when the engine heats up to running tem¬ 
perature the fit will be the same as with cast 
iron. 


PISTON RINGS 
Material 

Piston rings are made of cast iron, high 
in graphite, which tends to reduce wear es¬ 
pecially at high temperature. They are also 
made somewhat softer than the cast iron 
used in the cylinder walls, so that if there 



PISTON 

A. Lower piston ring. 

B. Piston skirt. 

C. Piston pin. 

D. Cross section of piston ring. 

E. Clearance about 1/32". 

F. Oil hole. 

G. Piston ring. 

H. Piston pin bushing. 

J. Connecting rod. 

K. Clamping screw. 

L. Safety wire. 

M. Piston head. 

N. Piston ring gap. 

The piston pin is clamped rigidly into the connecting 
rod. The piston pin bushing is pressed into the piston 
bosses. The third ring scrapes the excessive oil off the 
cylinder wall and forces it through the oil holes to the 
piston pin which lubricates the pin. Oil holes may 
be drilled in a like manner and convey the oil to the 
inside of the piston, which prevents an excessive amount 
of oil from being carried into the combustion chamber. 



FIG. 11 
PISTON 

A. Piston ring. 

B. Piston ring gap. 

C. Piston pin bushing (bronze). 

D. Clearance from .005" to .001". 

E. Clearance about 1/32". 

F. Oil relief groove. 

G. Oil hole. 

H. Piston pin boss. 

I. Oil hole. 

J. Oil groove. 

K. Oil groove. 

L. Connecting rod. 

M. Cross section of connecting rod. 

N. Lock nut. 

O. Piston pin locking screw. 

P. Cotter pin. 

Q. Cross section of ring. 

R. Piston skirt. 

S. Piston pin. 

T. Piston head. 

The piston pin is locked rigidly into the piston bosses. 
A bronze bushing is pressed into the connecting rod. 
The bearing is lubricated by the oil striking the head 
of the piston and dropping downward into the oil 
hole. The oil groove acts as a reservoir, maintaining 
a film of oil on the bearing surface. 













































































































































































































1(5 


ENGINES 


is any wear it will come on the small rings, 
which can be easily replaced. Cast iron also 
has a good spring effect, a natural tension, and 
when heated will therefore retain its spring 
tension better than steel or some other metal 
that would have to be tempered. Cast iron is 
also low in expansion, allowing the rings to be 
fitted tightly enough in the grooves to prevent 
a loss of compression when the engine is cold, 
and still not expand enough to stick when the 
engine is hot. 

These rings should fit freely enough into 
their grooves to allow them to expand and con¬ 
tract and have at all times only the tension of 
the ring holding them against the cylinder wall. 
When fitting new rings they are given about 
.0005" clearance in the groove. If a ring binds 
in it& groove there will be a loss of compression 
and excessive wear when the engine is hot. 
When the rings wear until they are loose in 
their grooves they will cause a knock or slap. 

The type of cut in a ring determines how 
closely the ends of the ring may be fitted. The 
principle of a leak proof ring is to close the cut 
or joint to prevent ,the fuel from going down 
into the crankcase and to prevent the oil from 
being drawn up into the combustion chamber, 
A certain amount of clearance must be allowed 
in this cut for expansion as the rings heat up, 
due to the fact that a ring will expand in its 
circumference, closing the gap. On a plain 
ring of three inch diameter, the clearance al¬ 
lowed is usually .005*", andl for every inch 
larger in diameter, allow .001" more clearance. 
On the so-called leak proof rings, there should 
be more clearance allowed. 

Ring Fitting 

To fit these rings, place the ring in the lower 
end of the cylinder and push it down about 
two inches with the piston, so that the ring 
will be properly aligned with the cylinder 
wall. Then take a thickness gauge and try 
the clearance in the cut. If the clearance is less 
than .005" on a 3" ring, remove the ring from 
the cylinder and file the ends. Care should be 
taken not to remove too much metal, other¬ 
wise there will be a loss of compression and 
a continuous fouling of the spark plug by 
the oil being drawn up through the cut. 
When replacing with new rings get the rings 
the same size as the cylinder. Rings 
can be obtained in steps of .005" larger than 
standard sizes, either in the diameters or the 
width. 

Rings .are not always made straight on 
the surface that engages with the cylinder 
wall, but may be tapered. The reason for 
this is that the rings going up and down will 
scrape the excessive oil off the cylinder wall. 
The upper ring is usually placed so that the 


widest part of the ring is towards the top to 
help scrape some of the oil up for lubrication 
of the upper rim. The center and lower rings 
are usually reversed, with the widest part 
of the rings down, to scrape excessive oil 
from the cylinder wall. When fitting rings, 
always see that there is clearance back of the 
ring—usually about 1/32"—so there will be no 
chance of the ring riding on the bottom of the 
ring groove.. 

PISTON PINS 

Material and Design 

Piston pins are usually made of high grade 
steel, heat treated and hardened, of a tubular 
type, or with a hole drilled through the center 
to make them light. After the pins are 
hardened, they are ground to as high a 
finish as possible. The piston pins are locked 
either in the piston or the connecting rod. 
Where the pin is locked in the piston, the upper 
or piston pin end of the connecting rod has a 
bronze bushing pressed into it to act as a bear¬ 
ing, and where the pin is locked in the con¬ 
necting rod by a clamping device, the bearings 
of the pin are in the piston. 

Fitting Piston Pins 

Piston pin bearings are usually made of 
bronze and pressed in, so that if they should 
wear too loose they can be removed and new 
ones installed. These bushings must fit in the 
piston or in the connecting rod very tightly, 
and should be reamed out with an expansion 
reamer to the same size as the pin. This 
will give a snug fit, just tight enough so that 
it may be pushed through with the palm of 
the hand without any play. The piston pin is 
lubricated either by the splash and spray from 
the interior of the engine or may be lub¬ 
ricated from the chamfer made in the lower 
ring groove which has holes drilled in it, lead¬ 
ing to the piston pin bearings. Again, in the 
full force feed oiling system the connecting 
rod has a tube soldered onto it leading up to 
the piston pin, thus lubricating the pin under 
pressure. 

When reaming piston pin bushings that are 
placed into the piston, care must be taken to 
turn the reamer straight through from one 
bushing into the other. Never ream one side 
and then turn the piston around and ream the 
other. The reason for reaming these bush¬ 
ings in this manner is to insure the holes being 
absolutely in line. 

A great many engines are ruined through 
carelessness in failing to lock the piston pin 
securely. The pin may be held by a bolt 
screwed into the piston, with a lock nut and 
cotter pin to prevent it from working loose. 



PISTON PINS — CONNECTING RODS 


17 


or it may be held in the connecting rod by the 
clamping lug and clamping screw. These 
screws are always doubly locked both by the 
tension of the fit and then with a cotter pin, 
or lock wire. Should these bolts become loose 
and drop out, they may get between the mov¬ 
ing parts and break the crankcase wall or 
spring the camshaft or crankshaft. If this 
occurs, the pin will work out of the piston 
against the side of the cylinder wall, and as 
the piston moves up and down, the hardened 
pin will score or groove the cylinder walls. 
These grooves in the cylinder walls allow the 
mixture to get by, causing a decrease in com¬ 
pression and temperature, condensation of 
fuel, mixing of fuel with the lubricating oil in 
the crankcase, causing the engine to wear 
faster and giving less power. 

The compression pressure is depended upon 
to help vaporize the fuel, consequently when 
there is a loss in compression, the fuel is 


not fully vaporized. Some of the fuel taken 
into the combustion chamber will not burn, but 
will pass through the scores down into the 
crankcase and dilute the lubricating oil. 
These scores will necessitate reboring, install¬ 
ing oversize pistons and oversize rings. When 
the piston pin becomes worn in its bearings it 
will knock very loudly. When the bushings 
become loose, they will also cause a knock. 
The piston pins can be ordered in different 
standard sizes for a particular type engine in 
steps of .005" oversize. 

CONNECTING RODS 
Material and Construction 

Connecting rods are usually made of high 
grade alloy steel, heat treated to toughen them 
and increase their strength. 

The upper end of the connecting rod carries 
the piston pin, and the lower end fastens 
around the crank pin on the crankshaft. The 





FIG. 12 


PISTON RINGS 


A. One piece ring (Diagonal cut). 

B. One piece ring (Step cut). 

C. One piece ring (Long Diagonal cut). 

D. Two piece (Diagonal cut). 


E. One piece (Special step cut). 

F. Two piece (Dowel pinned type). 

G. Two piece (Insert type). 

















































































18 


ENGINES 


lower end is a divided bearing, the connecting 
rod proper and the connecting rod cap. It is 
essential that the center line of the piston pin 
hole and the center line of the crank pin 
hole should be parallel. The connecting rods 
at times may become sprung, either through 
play of the crankshaft, burning out bearings 
and running loose, or they may have a natural 
tendency to warp. It is necessary to check the 
alignment of these holes, especially after re¬ 
scraping bearings or replacing with new ones. 
Both the piston pin bushing and the crank pin 
bearing are replaceable. 

Connecting rods in multiple cylinder engines 
should be as light as possible and all the rods 
in any engine should weigh approximately the 
same to within the fraction of an ounce. Con¬ 
necting rods that are unequal in weight result 
in an unbalanced condition, causing vibration. 


knocking and pounding, which affects the 
bearings. 

The bearings placed in the connecting rod 
and in the cap will loosen up at times, due to 
wear. They may be all babbitt, or they may 
be a bronze backed, babbitt lined bearing. 
Usually the babbitt is die cast and compressed 
when hot. The bearings may be held in with 
either dowel pins, rivets, or screws. Bearings 
are usually ordered from the manufacturer of 
the engine, giving the number and type of the 
engine. The connecting rod cap may either 
fit directly against the connecting rod proper 
or may have spacing shims or liners. The 
shims are placed there so that as the bearing 
wears, a thin shim can be removed and the cap 
tightened, to take the play out of the loose 
bearing, when the bearing is not worn enough 
to require replacement. Use care in removing 
shims to be sure that an equal number of the 



FIG. 13 


CONNECTING RODS 


A. 

Piston pin hole. 

I. 

Oil dipper. 

B. 

Clamping screw. 

J. 

Babbit bearing. 

C. 

Connecting rod. 

K. 

Crank pins. 

D. 

Connecting rod cap. 

L. 

Dowel pins. 

E. 

Connecting rod bolts. 

* M. 

Bronze bearing. 

F. 

Shims. 

N. 

Piston pin bushing (bronze) 

G. 

Castle nuts. 

0. 

Oil hole. 

H. 

Oil hole. 










































CONNECTING RODS 


19 


same thickness are taken from each side of the 
bearing. Some connecting rods will not have 
spacing shims, especially in an engine where 
the pressure oiling system is used. Care must 
be taken when placing these shims on the rods, 
that they do not come in contact with the 
crank pin surface. 

The connecting rod cap may be held on to 
the connecting rod proper by either two or 
four bolts. These bolts are usually made of 
heat treated alloy steel, and are very tough. 
Care should be taken when replacing connect¬ 
ing rod bolts, never to put in a soft steel bolt 
as it is liable to break. 

Bearing Fitting 

After fitting the bearings into the connecting 
rod and cap, fit the bearing to the crank pin 
for end play. There should be a small amount 
of end play in this bearing to allow for lubri¬ 
cation and prevent it from cutting ridges on 


the crank pin. Usually when fitting new bear¬ 
ings, they are given from .002" to .004" end 
play. They may come in the right width, or 
they may come too wide for the crank pin, 
necessitating extra fitting. After checking 
up for end play, see that the bearing does not 
rest on the fillets of the crank pin. These 
fillets are the rounded corners at the ends of 
the crank pin, where the crank pin connects 
onto the crank cheeks. After making sure that 
the connecting rod is not resting on the fillets, 
dress the connecting rod off close to the edge 
where it fastens onto the cap. With few ex¬ 
ceptions a bearing should never fit flush at the 
edge where it fastens together. This space is 
allowed as an oil retainer and also for the 
babbitt that is worn off to collect in, usually 
being about 1/64" deep, and about 1/8" down 
on the bearing surface. 

Scrape the babbitt off with a bearing 
scraper. Place the necessary number of shims 



FIG. 14 


CONNECTING RODS 


A. 

Blade rod. 

H. 

Cotter pin. 

B. 

Fork rod. 

I. 

Bronze bearing. 

C. 

Crank pin hole. 

J. 

Babbitt bearing. 

D. 

Piston pin hole. 

K. 

Dowel pins. 

E. 

Piston pin hushing (hronze). 

L. 

Oil dipper. 

F. 

Connecting rod bolts. 

M. 

Shims. 

G. 

Castle nuts. 



































20 


ENGINES 


between the connecting rod cap and the con¬ 
necting rod, so that the connecting rod will fit 
the same as when assembled into the engine, 
with all bolts drawn tight. Have just enough 
tension so that the weight of the connecting 
rod will swing it down if placed in a horizon¬ 
tal position. Never, when scraping bearings, 
fit a bearing tighter than it would be fitted 
into the engine. If the bearing should 
fit tighter it would spring it out of round, and 
when the bearing is fastened around the crank 
pin it will not have a full bearing surface. Af¬ 
ter fastening the connecting rod on the crank 
pin, work the connecting rod back and forth 
a few times to make an impression on the bab¬ 
bitt surface. The spots on the babbitt that 
are caused by rubbing the crankshaft are the 
high spots, and will appear bright when re¬ 
moved, or by placing Prussian blue on the 
crank pin, the high spots will appear blue when 
the rod and cap is removed. 


A bearing may appear to be machined ac¬ 
curately, but still there may be a variation in 
the machining • or variable hardness in the 
metal, and also the bearing may spring as it is 
placed in the connecting rod. The result is 
that the bearing will not fit evenly all over. 

These bearings are designed with a certain 
length and diameter, and have a certain area, 
to withstand the pressures and prevent exces¬ 
sive wear under operating conditions. Use 
must be made of all this area when fitting 
the bearing, therefore the bearings should be 
scraped down to a uniform bearing surface. 
Remove the connecting rods from the crank 
pin and notice the spots that are polished on 
the babbitt metal. These are the spots that 
are rubbing. If the bearing only touches in a 
few spots, it will be necessary to scrape these 
high spots down to have a greater amount of 
the surface in contact with the crank pin. 

Use a very sharp bearing scraper that 



BABBITTING AND CONNECTING ROD TESTING 


—c. 

FIXTURES 

Babbitt bearing. 

J. 

Anchor holes. 

D. 

Connecting rod. 

K. 

Babbitt space. 

F. 

Piston pin. 

L. 

Iron collar. 

G. 

Metal shaft. 

M. 

Set screw. 

AA. t 
BB. f 
A. 

Equal distances. . 3- 

-A. 

Fixture. 

Fixture. 

B. 

Square. 

D. 

Connectingrod. 

C. 

Babbitt bearing. 

E. 

Piston pin. 

D. 

Connecting rod. 

H. 

Bolt. 

E. 

Piston pin. 

I. 

Metal plug. 

J. 

Dowel pin. 














































CONNECTING RODS 


21 


has been honed on an oil stone. Dress down 
the high spots on the bearing, replace the 
connecting rod on the crankshaft and proceed 
as formerly, working it back and forth to ob¬ 
tain an impression. When scraping the bear¬ 
ing it will be noticed that the bearing surface 
becomes larger; that is, more spots are show¬ 
ing on the bearing, and as the spots increase, 
gradually let up on the heavy scraping and 
scrape more lightly. Care must be taken to 
scrape only the exact spots that show bright 
or blue. Do not scrape around the spot, as 
that will be cutting the grooves deeper and 
deeper, and no bearing will be obtained. 

The connecting rod should be held by hand, 
resting it against the chest, resting the fingers 
on the bearing and using very short strokes. 
It will take considerable time and practice to 
accomplish a good job of scraping, but an im¬ 
provement will be noticed each time, and better 
knowledge will be obtained of when to scrape 
hard and when to scrapf^ light. 

Alignment 

After scraping the bearing, the alignment 


should be checked in two ways. First, clamp 
the piston pin on to a surface plate and test it 
with a square to be sure it is perpendicular. 
Then place the connecting rod on the pin and 
check the crank pin bearing with the square. 
(See Fig. 15-3.) If it is out of alignment, the 
rod may be held in a vice and sprung with the 
aid of a wrench, using care not to spring it too 
far so that it will have to be sprung back. Too 
much bending tends to weaken the steel. 
Never heat a connecting rod as this also 
weakens the steel by destroying the value of 
the heat treatment given to toughen it. If the 
rod is bent too much to be straightened cold, 
replace with a new one. 

The final checking of alignment should be 
made with the rods on the crankshaft, and the 
pistons attached, as shown in Fig. 16. The 
bore of the cylinder is always square with the 
surface which joins the crankcase. The con¬ 
necting rod bearings must be fitted so that the 
piston pin is parallel with this finished surface, 
as at AA-BB, and the two squares A and B 
show that the piston is also absolutely true. 

A long connecting rod eliminates side thrust 



CHECKING THE ALIGNMENT OF CONNECTING 
RODS AND PISTONS 


A. 

Square. 

E. Machined surface. 

B. 

Square. 

F. Crankcase. 

C. 

Piston. 

AA.-BB. Equal distances. 

D. 

Piston pin. 













































22 


ENGINES 


on the cylinder walls. This side thrust causes 
excessive wear on the cylinder wall, on the 
piston, on the piston pin bearings and crank 
pin bearing. 

In racing engines, where thrust and speed is 
excessive, the distance between piston pin and 
crank pin centers is usually about twice the 
piston stroke. In general practice the rods 
may be somewhat shorter, as the long rod 
makes the whole engine high and heavy. 

The crank pin should be perfectly round, 
smooth, and straight. It will wear out of 
round through the continuous pounding. If 
it is necessary to tighten the crank pin bearing 
frequently it may be caused by the crank pin 
being out of round or by the piston pin and 
crank pin holes not being in proper alignment. 

When replacing the connecting rod in the 
engine while assembling, place it on the crank 
pin in the same position as when scraping, as 
the crank pin may be tapered. When fasten¬ 
ing the connecting rod into the engine while 
assembling, always tighten the nuts enough 
that there is no chance of their becoming loose, 
using a suitable size socket wrench, made es¬ 
pecially for this purpose. If the connecting 
rod should fit too tightly, NEVER BACK UP 
ON THE NUT to make the bearing fit properly. 
Either remove the cap and put in a thicker 
shim or else dress a little more from the bear¬ 
ing. Lock the castle nuts, which are pro¬ 
vided for that purpose, with a cotter pin; press 
the cotter pin in place and lock. It is very 
essential that these bolts should not become 
loose. If the connecting rod has the least 
chance to pound, all the strain will come on the 
bolt and nut and the bolt will break, allowing 
the connecting rod to be forced through the 
side of the crankcase by the whirling crank¬ 
shaft. A piston pin bearing or crank pin bear¬ 
ing that becomes loose will cause a knock. 
These bearings should be kept fairly snug, and 
if they become so loose that they will pound, 
they should be tightened immediately, other¬ 
wise they may break the connecting rod, the 
cap or the bolts. When a bearing becomes 
loose it will pound the crank pin out of round, 
or when the holding bolts and nuts become 
loose, it will break the bolts. 

Aircraft engine connecting rods and bear¬ 
ings are usually fitted looser. The reason for 
this is that through the tremendous friction 
resulting from the high speed and high bearing 
pressure there is more heat generated. This 
will cause expansion, and if clearance is not 
allowed for this expansion the friction and the 
heat will be greater, consequently the bearings 
Avill burn out, or the rod will break at the weak¬ 
est point. Many connecting rods have broken 
through bearings freezing or expanding until 
they seize the crank pin. 


On all bearings, there should be enough 
clearance allowed for expansion, and for a 
film of oil between the bearing surfaces. This 
oil reduces wear. A connecting rod bear¬ 
ing if fitted too tightly will wear the crank pin 
rough and out of round. Where no shims are 
provided for the fitting of bearings, it is nec¬ 
essary to scrape the bearings to a good fit, 
while scraping for a good bearing surface. 
When crank pins are lubricated by pressure 
system, usually no shims are used in the con¬ 
necting rod as they would allow oil to be forced 
out instead of covering the surface of the bear¬ 
ing. Bearing surfaces have oil grooves or oil 
retainers, except where the oil comes onto the 
bearing under a high pressure, so that as the 
crank pin revolves, it will always have oil upon 
it, either from the oil pipes directly, or from 
the dipper, as in the splash system. Where the 
connecting rods have dippers, dipping down 
into the oil trough, there will be a hole in the 
connecting rod cap bearings with oil grooves 
to distribute the oil over the bearing surface. 
These oil dippers should not dip into the oil 
more than from 1/16" to 3/32". If they dip 
deeper, the cylinder walls receive too much oil. 

V type engines sometimes have a yoke con¬ 
necting rod assembly, made up of two con¬ 
necting rods; one is the fork rod or outer rod 
holding the bronze backed, babbitt lined bear¬ 
ing; the other is the blade rod, which fits on 
the outside of the bronze bearing. From the 
assembly, it is seen that there are two bearing 
surfaces to be fitted. 

Fit the bearing into the fork rod first, the 
same as in the ordinary connecting rod, then 
proceed with the scraping as formerly. After 
the bearing is scraped so that the rod and the 
cap fit snugly together with the connecting 
rod bolts pulled up as tightly as possible and 
with the proper fit, then proceed with the fitting 
of the blade rod. This blade rod has no babbitt 
bushing on the inside, but fits directly on the 
outside of the bearing held into the fork rod. 
Care must be taken not to pinch this bearing 
with the blade rod. The blade rod should fit 
free with a nice rubbing fit. With an oilstone 
dress the bronze down to the correct fit. Some¬ 
times shims are placed between the blade rod 
and its cap, but it is not advisable. The yoke 
type rod is lubricated either by splash or 
pressure. 

In some V-type engines two rods side by side 
are used instead of the yoke type. In this case, 
the cylinders are not directly opposite each 
other, but staggered. These rods are fitted to 
the bearings same as any single rod. The 
hinged cap on the connecting rod is seldom 
used in automobile practice, as it has not 
proven successful. 



CRANKSHAFTS 


23 


Use of Soft Metal Bearings on Crankshafts 

The connecting rod bearings and main bear¬ 
ings are made of babbitt for several reasons. 

Babbitt containing a certain percent of anti¬ 
mony is very low in expansion. This will al¬ 
low the bearing to be fitted tightly enough to 
prevent a knock when the engine is cold and 
still not expand enough to grip when the en¬ 
gine is hot. Babbitt also containing certain 
percentages of tin and copper in addition to 
antimony is a soft bearing metal that will pro¬ 
tect the crank pin from excessive wear. That 
is, when the bearing is fitted too tightly, is 
overheated and expands from lack of proper 
lubrication, the wear always comes on the 
babbit instead of crank pin. This is preferable, 
because the bearing is much easier, quicker 
and cheaper to replace and refit than the 
crankshaft. 

CRANKSHAFTS 

The crankshaft is probably subjected to the 
greatest strain of any part of the engine, since 
practically the entire duty of transmitting the 
power of the engine to the driving wheels de¬ 
volves upon it. The three most important 
stresses are, that due to the pressure arising 
from the explosion, that due to the momen¬ 
tum of the reciprocating parts, and that due 
to the centrifugal force. It is a comparatively 
expensive part of the engine, requiring very 
accurate machine work. 

Material and Construction 

The material used for the construction of 
crankshafts is usually high grade alloy steel, 
heat treated to increase the strength. They 
are usually forged under a big drop hammer 
to the proper shape, roughly, then turned and 
finished evenly and smooth. Some crankshafts 
are made from a solid billet, blocked out, 
turned and finished all over. This, however, 
is an expensive process in automobile engine 
construction. 

The crank pin is offset from the center 
line of the main bearings to allow for an up¬ 
ward and downward movement of the piston. 
The distance from the center of the crank pin 
to the center of the main bearings is one-half 
the length of the stroke. 

Static and D3aiamic Balancing 

On account of the construction and shape of 
the crankshaft and the effects of the forces 
acting upon it, the shaft must be accurately 
balanced both statically and dynamically. 

Static balance means that if there is no one 
point on the crankshaft heavier than any other, 
after it is finished, it can be laid upon two 


parallel knife edges that have been carefully 
adjusted to horizontal position, and it will not 
move or rotate. But even though the crank¬ 
shaft has perfect static balance it may not have 
perfect dynamic balance. Crankshafts of dif¬ 
ferent construction will be out of balance at 
different speeds, even though the static balance 
is perfect. 

The crankshaft should be balanced at the 
average engine speed used in operating the car 
and to do this properly it is put in a testing 
machine and run at the normal engine speed. 
The centrifugal force due to the crank pin 
revolving around the center of the crankshaft 
would only tend to pull the shaft from the 
bearing in all directions, causing wear on the 
bearings. If the shaft is out of balance, how¬ 
ever, it will set up vibration and cause pound¬ 
ing and excessive wearing of the bearings. To 
overcome this a counterbalance is fastened on 
by bolts and dowel pins or forged integral with 
the shaft. The weight of the counterbalance 
is designed to offset the centrifugal force de¬ 
veloped in each crank pin, first from its own 
weight and the weight of the crank cheeks, 
and second from the weight of the reciprocat¬ 
ing parts attached to it. 

Another effect of this unbalanced condition 
is to cause the crank pins to creep toward each 
other as the centrifugal force springs the 
shaft. An exaggerated example of this creep¬ 
ing may be seen in the buffing wheel as the felt 
layers gather toward the center when the 
wheel is speeded up. This action brings undue 
strains on the bearings, tends to throw them 
out of alignment, and the binding of the bear¬ 
ings will use up some of the power to overcome 
the increased friction. The more main bear¬ 
ings on the crankshaft the less will be the 
creeping action in the shaft. 

Repairing 

Multiple cylinder crankshafts which are 
long, having in some instances as many as 
seven main" bearings, are very difficult to keep 
straight, if one is careless in the handling of 
them. Never stand a crankshaft on end, 
which, on account of the open space between 
the crank pins, gives the crankshaft a chance 
to sag. In sagging it pulls the main bearings 
out of line. Never drop a crankshaft down on 
its end; always lay it down carefully and fiat. 
If the crankshaft should be sprung a few thou¬ 
sandths of an inch, pulling up on the bearings 
will not make it all right. A crankshaft so 
adjusted will have a tendency to whip and 
wear the main bearings loose continuously. 

After removing the crankshaft from the en¬ 
gine, if it is not to be placed back immedi- 




ENGINES 


24 


ately, cover the bearings by wrapping oily rags 
around them to prevent metals of different 
kinds falling on the bearing surfaces, also to 
prevent the bearing surfaces from rusting. 

A crankshaft that is sprung should be 
straightened and reground, as a crankshaft 
that is out of line with the main bearings will 
continually wear the main bearings loose, 
causing a very heavy pound on sudden acceler¬ 
ation and application of the load. Crankshafts 
may be readily straightened when placed be¬ 
tween lathe centers or under a press. In case 
of a connecting rod breaking or any other 
part breaking and jamming on the inside of 
the engine as happens at times, it will put a 
twist in the crankshaft, which cannot be re¬ 
moved by ordinary straightening. Straighten 
the crankshaft as accurately as possible and 
then have it reground, which requires fitting 
it into smaller bearings. Should the crank pin 
become out of round from wear and pounding 
it will be necessary to regrind this in a grind¬ 
ing machine, although there are some hand 
tools made for straightening and truing crank 
pins. 

If no spacing shims are allowed between the 
main bearing cap and the main bearing, it 


is necessary to scrape the bearings down to the 
proper fit, besides having a good bearing sur¬ 
face. The bolts holding the main bearings are 
usually heat treated, having fine threads, and 
are locked by castellated nuts, provided for a 
cotter pin lock, or a safety wire. It is neces¬ 
sary that these bolts and nuts be locked. Either 
a cotter pin or safety wire should be used for 
this purpose. 

Alignment 

To check a sprung crankshaft, place it 
between the centers of a lathe or in a chuck 
and run the crankshaft in a steady rest, 
resting an indicator on the bearing surface. 
This indicator will indicate the point at which 
the crankshaft is sprung out of line and the 
number of thousandths of an inch that it is 
out. To check the accuracy and circularity 
of the main bearings or the crank pin use a 
micrometer. This is an instrument that will 
measure in thousandths, or ten-thousandths of 
an inch, and will show whether the crank pin 
is out of round or tapered. The crankshaft 
is mounted in the crankcase in babbit bear¬ 
ings, similar to the ones used in the connecting 
rods, to reduce friction and wear. 



Kemoi^e caps to adjust crank beannps and connecting rods. 
Remo/e 01/ ^p/asO p/ates before 
artemptmp to take out p/otons. 






Ma/n oil pipe 

Connectinif rod^^ Oil pump p/umfer 

sure to lock nuts n^'itti wire after makmp adjustments. 


FIG. 17 

CRANKSHAFT MOUNTING OF SIX CYLINDER ENGINE 


























CRANKSHAFTS 


25 


Pouring Bearings 

Both the main bearings of the crankshaft 
and the connecting rod bearings that fit on the 
crank pin may have to be poured. Bearings 
are poured where there are no die cast bear¬ 
ings available to replace them. When pouring 
connecting rod bearings it is necessary to 
make up a fixture with a pin the same size as 
the piston pin and a plug the same size as the 
crank pin, fastened onto a plate. After fasten¬ 
ing a connecting rod onto this fixture it will be 
necessary to pre-heat the jig and connecting 
rod. Babbitt should not be poured into a cold 
fixture because it will chill and not flow read¬ 
ily causing blow holes and cracked bearing 
surfaces. After these fixtures are heated up, 
pack whatever openings there are with either 
clay or powdered asbestos mixed with oil. 
Meanwhile heat up the babbitt in a ladle. The 
babbitt used should be of a high grade, high 
speed, bearing metal. Heat it in the ladle 
enough so that it will just char a soft pine 
stick, then pour the babbitt into the mold 
as rapidly as possible. After the babbitt 
has cooled in the connecting rod, remove 
the connecting rod and press the plug out. 
Then split the bearing with a hack saw and 
proceed with the scraping and dressing down. 

Main bearings are poured usually in the 
same manner, excepting that the crankshaft 
itself can be used. Rest the crankshaft on 
jacks, line it up with a surface gauge and in¬ 
dicator so that the surface of the crankshaft 
is parallel to the surface of the crankcase, 
checking up the gear centers at the same time, 
then heat the bearings on the crankshaft so 
that they are warm. Seal up whatever open¬ 
ings there may be with fire clay or asbestos 
mixed with oil and then pour the hot babbitt 
into the bearings one after the other. When 
it is cooled, remove the crankshaft and scrape 
these bearings down to a good fit and a good 
bearing surface. 

Fit shims in between the caps and the main 
bearings, otherwise when the babbitt is poured 
into the cap it will fuse on to the metal 
in the crankcase and the whole bear¬ 
ing will have to be melted out. The shims 
should be a thin metal or fabric shim, 
fitting against the crankshaft. After fitting 
in the shims, heat up the crankshaft and caps 
again, plug whatever opening there may be, 
pour one cap after the other, and when they 
are cool, remove them, and scrape in each 
cap separately and replace the shims with the 
correct size metal shims and see that they do 
not come in contact with the crankshaft. Care 
must be taken when pre-heating a rod or 
crankshaft not to get it too hot, destroying the 
heat treatment. 


Fitting of Bearings 

After replacing the bearings in the crank 
case for the crankshaft to revolve in, it will be 
necessary to scrape these bearings in order to 
utilize the full bearing surface. This is done 
in about the same manner as in scraping the 
connecting rod bearings. That is, the first 
operation will be to fit the crankshaft into the 
bearings for end play. 

Remove the bearing caps and place the 
crankshaft in the crankcase bearings. 
There should be from .002" to .004" end 
play to allow for expansion. If not enough 
clearance is allowed for expansion, the crank¬ 
shaft will cut the metal from the bearings and 
perhaps from the crankshaft proper, rough¬ 
ening the surface and causing excessive wear. 
The amount of clearance allowed for end play 
varies on different engines, depending on the 
speed, pressure and general power developed 
by the engine, but in automobile practice it 
is usually from .002" to .004". After checking 
up this end play, check up the different fillets 
to see that the crankshaft is not riding on 
these, because if the crankshaft is riding it 
cannot come down on the bearing surface. 

There is a thrust bearing always provided on . 
the crankshaft. This may be a ball thrust 
bearing, or the shoulder of the main bearing. 
Either the center bearing or, if on a multiple 
bearing crankshaft, one of the end bearings 
close to the flywheel will have a shoulder 
somewhat wider than the others. This 
shoulder is provided to take the crankshaft 
end thrust. It is not adjustable, and in case 
of wear, the whole bearing must be replaced. 
After checking up for end play and for riding 
on the fillets, then proceed with the scraping. 

The first thing to accomplish is to align the 
bearings, therefore do not scrape the bearing 
caps until all the bearings that are mounted in 
the crankcase are finished, especially on a 
multiple cylinder engine where there are sev¬ 
eral bearings. If one bearing should be higher 
than the others and the cap should be tight¬ 
ened down on the crankshaft, it would spring 
the shaft. Lay the crankshaft in the bearings, 
turn the crankshaft back and forth, getting an 
impression on the different bearings. Then 
scrape the bearings until a good surface is 
obtained on all of them, at least from a 75% 
to 80% bearing. 

Dress the bearings on the edge where the 
caps fasten on the bearing support, to allow it 
to act as an oil retainer and also allow 
space for the babbitt to collect as it wears. 
As the bearing surface improves under the 
scraping, do not scrape as heavily, but lightly, 
so as to obtain a good bearing surface. After 



26 


ENGINES 


the bearings have a good surface and the 
crankshaft rests upon all the bearings with the 
same pressure, then scrape the caps. Fit the 
caps the same as with the connecting rod caps, 
for end play and to prevent riding on the fillets. 
Then proceed with one cap at a time, scraping 
that cap to a good bearing surface. 

The life of the bearings in an engine always 
depends upon the finish and the area of the 
bearing surface. Care should be taken not to fit 
the bearings too tight, because a certain 
amount of clearance must be allowed for a film 
of oil, but if pains are taken in scraping a 
good bearing surface, a bearing will not have 
to fit so tightly as one that is improperly 
scraped. A bearing run without oil, or fitted 
too tightly, will cut and wear excessively. 
Some crankshaft main bearings have shims 
between the cap and crankcase to take up the 
wear. 

Clearance 

After the crankshaft is set up and has a good 
bearing surface, it should be free enough so 
that it can be turned by hand, not necessarily 
spinning around, but enough so that it can 
be turned freely. Aircraft and racing en- 
.gine crankshafts usually fit looser to allow 
for greater expansion. The amount of play al¬ 
lowed is usually taken up by expansion and 
a film of oil. A tight bearing will not al¬ 
low the oil to get onto the surface unless it has 
the pressure oiling system, and as so few au¬ 
tomobiles have the pressure oiling system, it is 
very essential that great care should be used in 
fitting the bearings. Always take into consid¬ 
eration the oiling system that provides the oil 
for the bearings. That will help to determine 
the clearance to allow on the bearings. 

VALVES 

T5T>es and Materials 

The two types of valves that are mostly 
used are the sleeve valve, as used in the 
Knight engine, and the poppet valve. Consider¬ 
able experimenting has been done on the 
rotary valve, but it has not proven successful 
on account of the expansion and difficulty in 
lubricating the exhaust valve. 

The poppet valve is constructed of different 
kinds of materials. There is the cast iron 
head valve, with a steel stem; the all-nickel 
steel valve, and the tungsten steel head with 
the nickel steel stem. The latter valve is 
generally used for the exhaust. The reason 
for the use of these different materials is 
that the material must resist warping and 
withstand the heat. Cast iron is one 
of the most successful materials used for 
valves, from the warping standpoint, but it 
will not stand the excessive heat generated 


in the racing or the aircraft engine, it 
having a tendency to burn. The tungsten 
steel valve will withstand heat and resist 
warping. 



FIG. 18 

TYPES OF VALVES 

A. Poppet valve. C. Rotary tube valves. 

B. Sliding sleeve valves. D. Rotary sleeve valves. 

The purpose of the valves is to allow the 
fuel to enter the combustion chamber at 
a certain time and to allow the exhaust or 
burned gases to escape at a certain time; and 
still when the piston is on the compression 
stroke and on the power stroke, these valves 
.must seal the combustion chamber. No mat¬ 
ter how true or how accurate the surface of 
either of the valves, or the seat in the cylinder 
is machined, there will be some unevenness 
there, which makes it necessary to frequently 
grind the valves into a perfect seat. 

Troubles and Repairs 

Valves sometimes warp, due to carbon 
packing underneath the seat, or excessive 
heat, making regrinding necessary. A leaking 
inlet valve may cause a back fire through 
the carburetor. Also there will be a loss of 
compression on the compression stroke, a gen¬ 
eral decrease in the efficiency through a.drop 
in temperature due to the loss of compression. 
Unequal compression in the different cylinders 
of the multiple cylinder engine will result in 
increased vibration. If the exhaust valve 
should leak it causes a general loss of com¬ 
pression but no backfire. 

Valve stems can be obtained in oversizes, 
in steps of .005" larger than the standard 
size. It is necessary that the valve stems 
fit the guide closely with a little clear- 


























































27 


VALVES 


aiice allowed for expansion. When fit¬ 
ting the valves, the exhaust valve stem 
should have .002" of an inch clearance, 
while the inlet valve stem should have 
.001" clearance, depending entirely upon the 
speed the engine runs. Aircraft engine 
valve stems are usually fitted looser than the 
valve stems in automobile engines. An inlet 
valve stem that is worn too much will cause 
an engine to miss fire at low engine speed, be¬ 
cause when the piston goes down on the suc¬ 
tion stroke with the inlet valve open and the 
throttle valve partially closed, as it will be at 
that speed, the inlet manifold and combus¬ 
tion chamber are under a high vacuum. This 
vacuum will draw air in through the worn 
valve stem guide, making the mixture to 
become too lean and cause backfiring through 
the carburetor. This can be tested by squirting 
some gasoline around the valve stem and as 
the piston goes down on the suction stroke 
it will draw this gasoline into the combustion 
chamber with the air, making the mixture 
richer or in the right proportion causing the 
engine to fire properly again. 

Valve Grinding 

When grinding valves, remove all free car¬ 
bon that is burned into the valves and valve 
seat and combustion chamber. Then be sure 
that the end of the valve stem is not resting 
on the tappet, otherwise it will be impossible 
to grind the seat. Use fine valve grinding 
compound, place a small amount on the face 
of the valve, drop the valve on the seat with 
a light spring underneath the valve head to 
lift it when the pressure is taken off the 
top of the valve. Use a screw driver or a 
prong made to fit the valve and turn the 
valve back and forth about a quarter of 
a revolution. Repeat this several times. Lift 
the valve by r^noving the pressure, turn it 
around about a quarter of a revolution to 
to pick out a new spot, then push the valve 
down onto the seat and turn it back and 
forth again as before. Care must be taken 
not to bear down too hard on the valve, other¬ 
wise ridges will be cut in it. A valve will grind 
in somewhat faster by having just a slight 
amount of pressure, moving it back and forth 
about a quarter of a revolution and continu¬ 
ously changing to a new spot on the seat so as 
to keep it round. 

Prussian blue can be used to check the ac¬ 
curacy of the valve surface. Remove all grind¬ 
ing compound from the valve and seat, put a 
small amount of Prussian blue on the valve 
face, wipe it off so there is just a faint coloring, 
then drop the valve down on the seat and turn 
it back and forth a few times. Lift the valve 
and see whether the correct blue impression 


has been made on the seat in the cylinder. 
It should show an impression all the way 
round; or use a soft pencil and mark the 
valve after it has been cleaned, drop the valve 
in the seat, again moving it back and forth. 
If the marks are erased all the way around 
it shows the valve to be seating properly. 
Then place the pencil marks on the seat in 
the cylinder and proceed as before. This is 
to check the seat in the cylinder, as the former 
process was to check the valve face. Should 
the test prove that the valve has a good seat, 
put some oil on the valve face and polish it by 
moving it back and forth as formerly. Place 
the valve back in the cylinder after removing 
all valve grinding compound placing the proper 
spring under the valve. Then readjust the 
clearance at the end of the valve stem to 
the proper dimensions given later. If any 
particles of this valve grinding compound 
should remain in the combustion chamber, 
it will work onto the cylinder wall and mar 
the finish, cutting the piston rings and cylin¬ 
ders, thus resulting in a loss of compression. 
Always replace the valve in the seat to which it 
was ground. 

Clearance 

The clearance at the end of the valve stem 
above the tappet is allowed for expansion. As 
the engine heats up the valves will heat up. 
If no clearance was allowed for expansion 
the valves would not seat. This clearance 
varies on different engines. Aircraft engines 
require sometimes as much as 1/32" clear¬ 
ance. Average clearances at the end of the 
valve stem are about .002" to .004" on the 
automobile engine. The clearance depends 
upon the heat developed by the engine. If too 
much clearance is allowed at the end of the 
valve stem, it will cause a knock and on a 
multiple cylinder engine if all the valves 
should have too much clearance it makes a 
noise that is very annoying. If the inlet 
valve should not have enough clearance at 
the end of the stem, it would cause a back¬ 
fire by the valve not seating, also causing a 
general loss of compression. If the exhaust 
valve does not seat properly by having too little 
clearance at the end of the valve stem, there 
will be a general loss of compression, caus¬ 
ing vibration, and perhaps the cylinder would 
misfire. 

The various automobile manufacturers 
specify certain clearances for their engines 
when they are cold. But there is a general 
rule that can be applied to any engine for 
clearances at the end of the valve stem. This 
clearance is adjusted by the adjusting screw 
in the top of the tappet which is held in place 
by a lock nut. 




28 


ENGINES 


Rule: Rough set all the tappets to about 
.020". Start the engine and allow it to run 
until it reaches its normal operating temper¬ 
ature. Then adjust the inlet valve clear¬ 
ance to .002" and the exhaust to .004". It is 
noticeable that when the engine cools off the 
clearance is greater, but it is necessary to 
have that much clearance there to allow for the 
expansion. This rule will hold true on any en¬ 
gine if the engine is heated up to its normal 
running temperature before making final ad¬ 
justments. Then check up the clearance when 
the engine is cold and that will determine the 
amount of expansion there is to the valve 
stems. 

After the clearance at the end of the valve 
stem has been adjusted properly, the lock nut 
should be locked securely. It will be noticed 
that as the lock nut is tightened it will 
move the adjusting screw upward consider¬ 
ably, perhaps for .003" or .004". This is due 


to the play of the screw in the thread in the 
top of the tappet. Allowance for this should 
be made when adjusting the clearance. Always 
test the clearance after the lock nut is tight¬ 
ened. 

Should a valve become warped or bent so 
badly that it cannot be ground, it may be 
necessary to reface it in a grinding machine as 
is used for the Tungsten steel valve. A cast 
iron valve can be refaced in a lathe or with a 
special hand facing tool, such as is commonly 
used in garages. If the guide for the valve 
stem is removable, the old guide may be 
pressed out and a new one pressed in. Some 
engines have no removable valve stem guides. 
It will then be necessary to ream the hole 
larger with an expansion reamer and put in a 
larger valve. With the removable guides all 
that is necessary is to replace the guide and 
use a standard valve. 




TAPPETS OR CAM FOLLOWERS 


A.A. 

Roller type. 


C. 

Clearance adjusting screw. 

H. 

Roller pin guide. 

B.B. 

Mushroom type—Flat 

head. 

D. 

Locknut. 

I. 

Roller pin. 

C.C. 

Mushroom type—Oval 

head. 

E. 

Tappet. 

J. 

Roller. 

A. 

Valve stem. 


F. 

Bronze bushing. 

K. 

Camshaft. 

B. 

Clearance. 


G. 

Tappet guide. 

L. 

Flattened portion 


tappet for adjusting. 





















































TAPPETS — ROCKER ARMS 


29 


TAPPETS OR CAM FOLLOWERS 
Types. 

There are several types of tappets. The ma¬ 
terials used are, as a rule, heat treated steel, 
ground and machined to a very smooth sur¬ 
face. These tappets are fitted with screws for 
the purpose of adjusting valve clearances. The 
method of adjustment varies with the make, 
but in all cases is for the purpose of allowing 
valves to come to a full seat before the tension 
is released on the tappet. The tappets are 
equipped with some device for locking the 
adjusting screw so that when the engine is in 
operation, continuous pounding upon the tap¬ 
pets will not loosen the screws and change 
the relative adjustment of the valves. The 
device used for locking is usually a simple 
jam nut. The top of the tappet is drilled and 
threaded, into which screws an ordinary hard¬ 
ened cap screw. The lock nut is placed on the 
upper threads of the cap screw. 

Tappet guides are generally bushed with 
bronze bushings. Occasionally they are simply 
a part of the crank case. They are lubricated 
through oil grooves or oil outlets through the 
crank case. However, the entire valve cham¬ 
ber may be lubricated by splash. The oil dip¬ 
per throws the oil through the upper portion of 
the engine. These tappets sometimes become 
worn and have a tendency to make a very 
objectionable knock. The knock is not danger¬ 
ous, but will cause an unnecessary amount of 
noise and wear. 

A push rod is a continuation of the tappet, 
connected to the rocker arms, valve lifters or 
roller arms, which operate directly on the valve 
stems. This is most commonly used in over¬ 
head, or 1-type engines. The material used 
in push rods is, as a rule, heat treated steel, 
being ground and accurately finished to length. 
The push rods tend to rattle and knock if 
their sides become worn. They are lubricated 
much in the same way as tappets. Clearance 
for push rods or tappets in their guides should 
not be over .001". 

ROCKER ARMS 

The purpose of the rocker arm is to make 
the overhead connection between the push rod 
and valves. This rocker arm is usually a steel 
forging, having its fulcrum or bearing at the 
rocker arm post, and usually employing a 
bronze bearing on the inside. Remove the 
bearing when worn and replace with a new one. 
Some engines have the rocker arm mounted 
on annular ball bearings. The rocker arm 
pin is usually made of alloy steel, hardened 
and ground to reduce the wear and friction 
to a minimum. The outer end of the rocker 
arm that connects to the push rod may have 


a hinge joint with the clearance adjusting nut 
below the hinge. This hinge joint necessitates 
a hinge pin which is also hardened and ground. 
Sometimes the upper end of the push rod is 
rounded off similar to a ball, with a concave 
receptacle at the outer end of the rocker arm, 
making a so-called ball and socket type bear¬ 
ing. The end of the rocker arm that operates 
the valve may be just a flat surface, so 
that it slides on the end of the valve stem, 
or it may have a roller on the end, operating 
on a hardened pin. The roller is usually made 
of high carbon steel, heat treated and ground 
to reduce wear and insure accuracy. 

VALVE SPRINGS 

The valve springs of both inlet and exhaust 
valves are* held onto the valve stem by a spring 
cup, or retainer, which is a grooved receptacle 
to center the spring and hold it. This spring 
cup may be held on the valve stem by any one 
of several methods. One is by screwing the 
valve spring cup onto the valve stem and 
then locking it with a cotter pin. Another is 
by having a groove cut in the valve stem, a key 
inserted and held in place by the lower side of 
the retainer. Another, which is most common, 
is by a horseshoe washer, fitting into a groove 
cut around the valve stem. To replace these 
valve springs or remove them from the valves, 
turn the flywheel so that the tappet comes 
down on the lowest part of the cam. Use a 
valve lifter, which is a forked bar suspended by 
a chain or in some other simple manner, place 
it under the spring cup, lift the retainer up¬ 
ward, remove the lock and let the spring 
down. Then remove the valve from the cham¬ 
ber and lift the spring out of place. The same 
process is followed when replacing valve 
springs except that the operations are re¬ 
versed. Place the valve spring into place first 
with the retainer underneath, then drop the 
valve into place. Get the valve lifter under¬ 
neath the retainer, lifting the spring, retainer 
and spring upward, insert the lock into the 
groove or slot and then let the retainer down 
onto the retainer lock. 

Usually both valve springs have the same 
tension, although it is not necessary that they 
should have. Spring pressure is usually about 
thirty-five pounds; it may be more or less, de¬ 
pending upon the amount of suction desired in 
the combustion chamber and also upon the 
speed at which the engine runs. The spring 
under all conditions, either exhaust or inlet, 
should always be stiif enough or of high 
enough pressure to keep the valve and tappet 
riding on the cam at the high engine speeds, 
otherwise when the valve closes with a weak 
spring, the crankshaft will have passed the 
proper closing point. 



30 


ENGINES 


Racing engines require considerably more 
spring pressure on both valves. The inlet 
spring pressure need not be quite as much as 
the ‘exhaust, because the inlet valve does not 
have a tendency to be drawn away from its 
seat, during intake stroke, as it is already 
open. As the piston goes down on the intake 


stroke if the exhaust spring should be weak, 
the exhaust valve will be drawn away from its 
seat by the suction of the piston, and burnt 
gases will be drawn back into the combustion 
chamber, weakening the new charge, causing 
a general loss of power and misfiring. The 
inlet spring need only be strong enough so 



I-HEAD CYLINDER AND DETAIL OF VALVE 
CAGE ASSEMBLY 


1. 

Valve cage. 

C. 

Water jacket. 

2. 

Cage seat. 

D. 

Connecting rod. 

3. 

Valve head. 

E. 

Piston. 

4. 

Valve seat. 

F. 

Combustion chamber. 

5. 

Valve face. 

G. 

Port. 

6. 

Valve stem. 

H. 

Inlet manifold. 

7. 

Valve stem guide. 

1. 

Exhaust manifold. 

8. 

Port. 

J. 

Valve cage. 

9. 

Cage nut. 

K. 

Cage nut. 

10. 

Cylinder head. 

L. 

Valve spring. 

A. 

Crankcase. 

M. 

Valve spring retainer. 

B. 

Cylinder. 

0. 

Rocker arm. 


P. Rocker arm post. 

Q. Rocker arm shaft and bearing. 

R. Oil holes and retaining felts. 

S. Ball and socket joint. 

T. Push rod adjustment. 

U. Push rod. 

V. Lock nut. 

W. Tappet. 

X. Tappet guide. 

Y. Tappet roller. 

Z. Cam. 
























































































































VALVE ARRANGEMENTS 


31 



F-HEAD CYLINDER SHOWING TWO DIFFERENT 
TYPES OF VALVE MOUNTING 


A. 

Clearance. 

N. 

Push rod. 

1. 

Crankcase. 

B. 

Valve spring retainer. 

O. 

Pet cock. 

2. 

Tappet guide. 

C. 

Valve spring. 

P. 

Cylinder head. 

3. 

Tappet bushing. 

D. 

Valve stem guide. 

Q. 

Exhaust manifold. 

4. 

Tappet. 

E. 

Cage. 

R. 

Exhaust port. 

5. 

Lock nut. 

F. 

Inlet port. 

S. 

Valve inspection plate. 

6. 

Clearance adjusting nut. 

G. 

Inlet manifold. 

T. 

Inspection plate retaining nut. 

7. 

Clearance. 

H. 

Rocker arm. 

U. 

Crankcase. 

8. 

Valve spring retainer. 

I. 

Rocker arm post. 

V. 

Camshaft and bearing. 

9. 

Valve spring. 

J. 

Oil reservoir. 

W. 

Piston. 

10. 

Valve stem and push rod guide. 

K. 

Felt oil retainer. 

X. 

Connecting rod. 

11. 

Water jacket. 

L. 

Oil hole. 

Y. 

Water jacket. 

12. 

Cylinder head gasket. 

M. 

Ball and socket bearing. 

Z. 

Combustion chamber. 

































































































































































































































32 


ENGINES 


that the valve stem and tappet will always ride 
on the cam. Generally the exhaust valve 
spring has the more pressure, so if the inlet 
spring has the same pressure as the exhaust 
there is more than sufficient spring pressure 
on the inlet, causing a slight loss of power. 
On engines where the valve springs are of 
different lengths, the longest spring or the one 
with the most pressure is the exhaust. 

The automatic inlet valve is not opened by 
a cam, but by the suction of the piston, and 
is closed by a light spring. This light spring 
allows the valve to be drawn away from its 
seat on the suction stroke, and as the suction 
decreases the valve will gradually seat itself 
aided by the spring. Then the piston moving 
up on the compression stroke with both valves 


closed, compresses the mixture. The spring 
tension required on the valve is small and has 
therefore perhaps 1/8" or 3/16" lift. The 
valve chatters considerably on its seat; it is not 
a very practical valve to use in automobile 
practice, being very noisy. 

VALVE CAGES AS USED IN OVERHEAD 
ENGINES 

The valve cage may be used on either the 
I or the F-head engine in connection with 
the overhead valve. These cages are used 
so that the valves may be readily removed 
for regrinding. If the valves are, set di¬ 
rectly in the head of the cylinder on the I-head 
where the head is not removable, it would 
be necessary to remove the whole cylinder 





ya/re push rod 

Inlet ralre hfter 
Yalre f/fter quide 


In/et raire 
i^t/nder head 


Cam shaft 


Release damp sere 
at side and adjust 
here. 


Vdire push rod 


'Inle f rat re spnnq - 

Inlet rat re stem 
Gphnder 

Eo'haust ratre. 


Yalre spr/nq 
seat p/n 
Yalre sprimii 
seat 
Exhaust ratre 
hfter—- 


Exhaust rafre 
stem cjuide 


"Exhaust ratre 
spr/np 

M'Clearance 
'xhaust ratre hfter 
adjust/nq screrv. 
Exhaust ratre 
f/fter lock 
nut 


\ 


FIG. 22. 

VALVE OPERATING MECHANISM OF A TYPICAL 
F-HEAD CYLINDER 




























VALVE ARRANGEMENTS 


33 



FIG. 23 

L-HEAD ENGINE SHOWING AN ENLARGED VIEW 
OF VALVE ASSEMBLY 


A. 

Crankcase. 

P. 

Exhaust manifold. 

4. 

Valve face. 

B. 

Crankshaft. 

Q. 

Inlet manifold. 

5. 

Valve stem. 

C. 

Shims. 

R. 

Valve stem guide. 

6. 

Valve stem guide. 

D. 

Main bearing cap. 

S. 

Valve spring. 

7.. 

Valve stem bushing. 

E. 

Main bearing adjusting nut. 

T. 

Valve spring retainer. 

8. 

Port. 

F. 

Main bearing stud. 

U. 

Clearance. 

9. 

Water jacket. 

G. 

Camshaft bearing. 

V. 

Clearance adjusting screw. 

10. 

Valve cover plate. 

H. 

Camshaft bearing lock. 

W. 

Lock nut. 

11. 

Gasket. 

I. 

Valve cover plate. 

X. 

Tappet. 

12. 

Valve spring. 

J. 

Cylinder head gasket. 

Y. 

Tappet guide. 

13. 

Valve spring retainer. 

K. 

Cylinder head stud. 

Z. 

Camshaft. 

14. 

Horse shoe washer. 

L. 

Cylinder head nut. 

1. 

Combustion chamber. 

15. 

Valve stem. 

M. 

Spark plug. 

2. 

Valve head. 

16. 

Cylinder head. 

N, 

Water jacket. 

3. 

Valve seat. 

17. 

Cylinder head gasket. 

0. 

Combustion chamber. 














































































































































34 


ENGINES 


block from the engine to regrind the valve, but 
by placing the valves in a cage arid holding 
the cage in with a nut, or by screwing the cage 
onto a seat, it eliminates removing the whole 
cylinder to regrind the valves. These valve 
cages are either threaded into the cylinder or 
held down with a nut against a machined seat 
or gasket. The valve must be ground to a seat 
in the cage. Sometimes the cage requires 
grinding. 

Care must be taken in placing the cage into 
the cylinder that the port holes are in line with 
the ports in the cylinders, otherwise the pas¬ 
sage is obstructed, or partially obstructed. 


causing a loss of power and perhaps misfiring 
in the cylinder. These valve cages are made of 
cast iron, having the valve stem guides reamed 
to the correct fit. The valve cage is used suc¬ 
cessfully on automobile engines, but not with 
racing or aircraft engines, the reason being 
that the heat in the automobile engine is not as 
great as it is in a racing or an aircraft engine. 
The cage not being used on the latter engines, 
it is then necessary to remove the cylinder to 
regrind the valves. 

If the inlet valve cage leaks at its seat, the 
piston while going down on the suction stroke 
draws in excessive air making the mixture too 



FIG. 24 

GENERATOR AND CAMSHAFT DRIVE 







VALVE CAGES — CAMSHAFT DRIVE 


35 


lean, causing misfiring and backfiring, while 
the exhaust port when it leaks, causes a hiss¬ 
ing noise, loss of compression, efficiency and 
power. 

VALVE SPRING COMPARTMENTS 

The compartment where the valve springs 
are located, is on the outside of the cylinder 
casting, with a cover fastening onto the cylin¬ 


der, having a gasket to prevent leakage. This 
chamber has an opening into the crank case to 
allow the vapor from the crank case to lubri¬ 
cate the tappets and valve stems. The covers 
are generally held on with a long stud which is 
fastened to the cylinder casting. The gasket 
is usually make of cork. On the multiple 
cylinder engine one cover plate may enclose 
all of the valves, although some engines 


FIG. 25. 



CHAIN DRIVE AND METHODS OF ADJUSTMENT 


This figure shows the chain drive 
for the camshaft and the generator, 
and the method of removing the 
slack in the chain. 

With the chain drive, all the 
shafts turn in the same direction. 
In the illustration to the left, (D) 
represents the generator mounting 
which is pivoted at the bottom and 
slotted at the top, so that it may be 


swung either to the right or left, 
for the purpose of adjusting the 
tension of the chain (C). (A) 

represents the camshaft sprocket 
and (B) the crankshaft sprocket. 
In the illustration at the right (E) 
represents the generator sprocket; 
the generator hub (H) is mounted 
in the gear case (I). (J) repre¬ 

sents the generator shaft set off 


center, so that when the generator 
is turned it will swing the shaft 
inward or outward. 

(A) represents the camshaft 
sprocket and (B) represents the 
crankshaft sprocket. (C) repre¬ 
sents the chain. (F) represents 
the spiral gear that drives the 
ignition distributor shaft (G). 




FIG. 26. 


DIRECTION OF ROTATION OF TIMING GEARS 

This figure shows the different gear arrangements 
on 4 cycle engines. 

The direction of rotation of the timing gears and the 
number of gears in the gear train must be known to 
properly time the camshaft. 

When there is no idler gear between the crankshaft 
and camshaft timing gears, the gears revolve in oppo¬ 
site directions. 

When there is an idler gear between the crankshaft 
and camshaft timing gears, the timing gears revolve in 
the same direction. 

A. Crankshaft timing gear or master gear. 

B. Camshaft timing gear. 

C. Idler gear. 


















































36 


ENGINES 


have two or more cover plates for the spring 
compartment. 

CAMSHAFT AND ECCENTRIC SHAFT 

The camshaft is a shaft used to lift the valves 
from their seats at the proper time. The cams 
are either placed on the camshaft and held 
tight with keys or pins, or forged integral with 
the shafts, and then ground to the proper de¬ 
gree of accuracy. The eccentric shaft is a 
shaft that is used in the sleeve valve engine to 
move the sleeves up and down, causing the 
ports to be uncovered. Either a camshaft or an 
eccentric shaft is used in the four stroke cycle 
engine, and revolves one-half as fast as the 
crankshaft, or while the crankshaft is turning 
two complete revolutions the camshaft turns 
one. This is because the four stroke cycle en¬ 
gine requires two revolutions of the crankshaft 
to complete the cycle of operations. The gear 
or sprocket on the camshaft has twice as many 
teeth as the gear or sprocket on the crank¬ 
shaft. The gears or sprockets are fastened 
onto the end of the camshaft with bolts or 
keys. These gears must have a small amount 
of backlash or Clearance, wiiere the teeth mesh 
with each other. This clearance is from .002" 
to .004", just enough play to allow for expan¬ 
sion, and for any unevenness in the contour of 
the teeth. 

The camshaft revolves in bearings made of 
bronze or babbitt metal w’hich are mounted or 
pressed into the crankcase. These bearings 
must be in line with one another so as to allow 
the shaft to revolve freely. The camshaft is 
usually about .001" smaller than the bearing 
and should have very little end play, preferably 
from .002" to .004". It is made of steel, 
heat treated, hardened and accurately ground. 

The part of the cam that has a true 
radius, concentric with the shaft, is called 


the heel, while the part of the cam that 
is used to raise the valves is called the toe. 
On engines w^here the intake, or suction stroke, 
is 205° long, crankshaft travel, the toe of the 
cam is 102 1 / 0 ° long, because the camshaft 
travels one-half as fast as the crankshaft. If 
the exhaust stroke is 230° long, the exhaust 
cam toe will be 115° long. The toe or lift of the 
cam governs the height the valve is lifted 
from its seat, the length of time the valve is 
held open (the stroke) and the speed of the 
opening and closing of the individual valve. 

The camshaft for a single cylinder engine 



EXHAUST AND INLET CAMS—RELATIONSHIP 



This figure shows the design of an inlet cam for an shafts in the four stroke cycle engine revolve at one half 
engine having the intake stroke 205° long and an ex- crankshaft speed the toe of the cams are just one half 
haust cam for an exhaust stroke 230° long. As the cam- the length of the crankshaft travel in degrees. 


























CAMSHAFT 


37 


with both valves operated mechanically has 
two cams on it. On multiple cylinder engines 
the order in which the cams are placed on the 
camshaft governs the order in which the valves 
open and the cylinders fire. The cylinders are 
numbered 1, 2, 3, etc., beginning at the front or 
cranking end of the engine, and the order in 
which they fire is called the firing order of the 
engine. Then to find the firing order of an 
engine, it is necessary to determine the order 
in which the cams are set on the camshaft or 
the order in which the valves open, remember¬ 
ing that the valves open just twice as many 
degrees apart crankshaft travel as they do 
camshaft travel. Knowing this to be true 
then, to determine the number of degrees 
apart the cams are set on the camshaft, divide 
the number of degrees apart the cylinders fire, 
crankshaft travel, by two. 

Example: In a 4-cylinder engine the cylin¬ 
ders fire 180° apart crankshaft travel, and all 
inlet or exhaust cams are set 90° apart on the 
camshaft. If this engine should have a 1-2-4-3 
firing order, number 1 and 4 cylinders would 
fire 360° apart crankshaft travel, 180° apart 
camshaft travel, and number 1 and 4 cams, 
either inlet or exhaust, would be set 180° apart. 

INLET VALVE OPENING AND CLOSING 

The degrees which are considered in this ex¬ 
planation will be the position that the crank¬ 
shaft is in when the valves either open or close. 


The valve opening and closing points are not 
standard, for the reason that there are several 
conditions that are considered in determining 
these points, such as speed of the engine, fuel, 
size and lift of valves, size of the combustion 
chamber, stroke, shape of inlet manifold, inlet 
port, exhaust port, diameter and length of ex¬ 
haust pipe. 

The suction stroke is determined by the 
opening and closing of the inlet valve. 
As long as the inlet valve remains open 
the piston is on the intake stroke. The in¬ 
let valve opens when the crankshaft is about 
10° past top dead center, and closes when the 
crankshaft reaches a point approximately 
35° past bottom dead center. Some inlet 
valves open on dead center, or may open as 
late as 30° past top dead center. Some inlet 
valves close as early as 15° past bottom dead 
center and others as late as 45° past bottom 
dead center. The reason for closing the in¬ 
let valves so late after the piston has started 
upward, is that the gases, coming in during the 
suction stroke, attain a certain momentum. 
The faster the piston goes down on the suction 
stroke, the greater will be the velocity of the 
gases rushing into the combustion chamber. 
When the pressure of the gases rushing in 
equals the pressure formed by the piston mov¬ 
ing upwards, the inlet valve should close. On 
high speed engines the inlet valve is held open 



FIG. 29 

CAMSHAFT MOUNTING, FOUR CYLINDER ENGINE 

















38 


ENGINES 


longer, due to the greater velocity of the 
incoming gases, while on the low speed en¬ 
gine the inlet valve is closed earlier because of 
the lower velocity of the incoming gases. 

Theoretically the valve timing is not perfect 
for all engine speeds, but the valve timing that 
is used is the one that has been experimented 
with at the average speed of the car so as to 
give the highest efficiency. The inlet valve 
usually opens a few degrees after the exhaust 
valve has closed so that the piston will move 
downward a trifle with both valves closed and 
form a partial vacuum in the combustion 
chamber. This vacuum, as the inlet valve 
opens, will draw the gases in much faster than 
if it had been open when the suction started. 
The speed of the gases rushing through the 
inlet manifold helps to properly vaporize the 
fuel. 


EXHAUST VALVE OPENING AND CLOSING 

The exhaust valve usually opens about 45° 
before bottom dead center, although this open¬ 
ing will vary a few degrees either way, depend¬ 
ing upon the speed of the engine and the back 
pressure in the cylinder and the exhaust pipe. 
The exhaust valve closes when the piston 
reaches top dead center or a few degrees past. 
The size and lift of the exhaust valve and the 
back pressure generally determine the point of 
opening, because if the exhaust valve should 
open too late on a high speed engine, for in¬ 
stance, the piston as it moves up on the ex¬ 
haust stroke would have to work against the 
pressure that is in the combustion chamber 
and in the exhaust manifold. By allowing 
the gases to escape from the cylinder earlier 
this pressure is relieved. 

The exhaust valve may close on either top 



FIG. 30 


CYCLE OF OPERATIONS 


This figure shows the combination of the four strokes 
and in the order in which they occur in an engine 
with crankshaft turning in a clockwise direction. 

Assuming that both valves are closed as the crank¬ 
shaft reaches a point 10° past top dead center, the inlet 
valve starts to open and the piston moves downward 
on the intake stroke. This valve remains open during 
205° of crankshaft travel until a point 35° past bottom 
dead center, at which point the inlet valve closes. 

The piston moves upward (both valves being closed) 


during the next 145° of crankshaft travel, until it reaches 
top dead center, at which time the spark occurs. 

The piston is forced down on the power stroke during 
the next 135° of crankshaft travel, to a point 45° before 
bottom dead center, at which time the exhaust valve 
opens. 

The exhaust valve remains open until 5° past top dead 
center or during 230° of crankshaft travel. 

After the exhaust valve closes there is 5° of crank¬ 
shaft travel before the inlet valve opens again. 





















VALVE OPENING AND CLOSING 


39 


dead center or a few degrees past, which may 
be necessary to insure all the burned gases 
having left the cylinder. With the general 
variation in the opening and closing of the 
valves it can be seen that the four strokes will 
be of different lengths. Consequently, the 
cams will be made differently. For instance, 
in the valve opening and closing just given, the 
exhaust stroke is about 230° long, while the 
intake stroke is about 205° long, necessitating 
different shape cams for the inlet and for the 
exhaust. 

The ideal type of cam for maximum power, 
is one that opens the valves to the wide open 
point as soon as possible, holds them open as 
long as possible, then closes them quickly. A 
cam of this type operates very noisily. Cams 
on automobile engines are usually made with 
a slight curve ground on the toe. The shape 
of the tappet, or cam follower that rides on the 
cam has considerable to do with the speed at 
which the valves open and close. A tappet 
with a roller riding on the cam will be one 
of the slowest acting tappets, but the quiet¬ 
est, while a tappet that is flat on the bottom 
will open very quickly but is noisy. In auto¬ 
mobile engine construction it is necessary to 
sacriflce some of the maximum efficiency to 
obtain quietness. 

MANIFOLDS 

Material and Construction 

The inlet manifold is designed with two im¬ 
portant considerations: first, to give each 
cylinder the same quantity of fuel, and second, 
to insure the mixture being equally well vapor¬ 
ized when entering each cylinder. With the 
fuels used today, a great portion of it passes 
through the manifold as a mist suspended in 
the air current. Since the velocity of the air 
depends upon the speed of the engine, the size 
and shape of the manifold has much to do with 
the mixing of the gases. Bends, sharp cor¬ 
ners and rough surfaces on the interior of 
the manifold have a tendency to retard the 
fuel mixture and cause condensation. 

The inlet manifold is made of aluminum, 
malleable or cast iron, and a part of it is some¬ 
times cast integral with the cylinders, where 
the cylinders are in block. It may also be cast 
integral with the exhaust manifold so that the 
incoming gases may come in contact with the 
hot walls of the exhaust passages, heating 
them and causing them to vaporize more 
thoroughly. It may be water jacketed allow¬ 
ing a circulation of hot water around it, or it 
may be oil jacketed, serving two purposes, to 
heat the gases and also cool the oil that cir¬ 
culates around it. The fuel may be mixed in 
the carburetor with hot air drawn from around 
the exhaust pipe. All these heaters, hot spots 


and hot air tubes have a tendency to improve 
the thermal efficiency of the engine by warm¬ 
ing up and vaporizing the fuel better. When 
the gas is cold and taken into the cylinder in 
a partially vaporized state the unvaporized 
portion does not burn, but is lost or wasted, 
washing the lubricating oil from the cylinder 
wall, getting down into the crankcase, mixing 
with the oil, spoiling its efficiency as a lubri¬ 
cant and causing loss of compression and 
power. 

When the air velocity is high, it chills the 
manifold enough to cause frost to form on the 
exterior on damp cold days. This is not an 
indication of a poor mixture; it has only to do 
with the atmospheric conditions outside the 
manifold. 

The principal considerations with the ex¬ 
haust manifold are to take the exhaust gases 
away from the cylinder as quickly as possible 
and to make it of such size as to avoid any 
back pressure in the cylinder. The quicker the 
exhaust gases are expelled the less heat they 
will give up to the cylinder casting. It is sel¬ 
dom cast integral with the cylinders but is 
bolted on with long studs and clamp arms. 

A gasket usually made of a sheet of asbestos 
between two sheets of copper is used to take 
up the unevenness between the face of the 
manifolds and the cylinders. 

Troubles and Repairs 

The inlet manifold gaskets must be air 
tight, otherwise when the piston moves down 
on the suction stroke it will draw air in 
through these openings, making the mixture 
too lean and causing misfiring and possibly 
backfiring through the carburetor. To test 
an inlet manifold for a leak, run the engine 
as slowly as possible. With a priming can 
squirt gasoline on the various joints, or any 
point where a leak is suspected. As the gaso¬ 
line is squirted on a joint where air is drawn 
in, the gasoline will be drawn in, enrichening 
the mixture, allowing the cylinder to fire 
again, causing the engine to run faster. If 
the gasoline is squirted on a joint that does 
not leak, it will have no affect on the running 
of the engine. 

In time carbon will obstruct the passages 
in the exhaust manifold due to the burned 
gases passing through, necessitating cleaning. 
The back pressure caused by the formation 
of carbon is effective on the top of the 
piston, having a tendency to hold it back 
when the piston comes up on the exhaust 
stroke, causing a loss of power. These mani¬ 
folds may crack, and if they do it will neces¬ 
sitate welding. If the casting warps in the 
welding process the flange surfaces may re¬ 
quire reflnishing. Care must be taken not to 




40 


ENGINES 


have the gasoline supply line too close to the 
exhaust manifold. In case of leakage the gaso¬ 
line would be ignited, and set fire to the car. 
Insulate the exhaust manifold at this point 
with asbestos. 

VALVE CHAMBERS OR PORTS 

The valve chamber leading either to the inlet 
valve or exhaust valve may feed to two or 
more cylinders, with the valve closing off 
each separate cylinder. These passages 
should be as smooth as possible and with few 
curves and obstructions. The inlet manifold 
when clamped onto the cylinder at the valve 
chamber should line up with the port, other¬ 
wise the passage is obstructed, interfering with 
the free flowing of the gas. 

FLYWHEELS 

The purpose of the flywheel is to store up 
the energy imparted to the crankshaft by the 
explosion in the cylinder and keep the shaft 
turning between the impulses so that the turn¬ 
ing force may be substantially uniform. 

With a single cylinder four stroke cycle en¬ 
gine, the power is applied for only one stroke 
and there are three idle strokes. Thus the fly¬ 
wheel stores up some of the mechanical energy 
developed during the power stroke and gives it 
up in keeping the shaft turning until the next 
power stroke. As the number of cylinders is 
increased, the impulses occur oftener and a 
smaller amount of weight is required in the 
flywheel to keep the shaft turning. 

Using the weight of flywheel required for a 
single cylinder engine as 100%, the weights for 
other engines are approximately as follows: 


Single . 100% 

Two cylinder . 80% 

Four cylinder. 44% 

Six cylinder . 22% 

Eight cylinder . 11% 

Twelve cylinder. 4% 


These weights are usually exceeded in actual 
practice to facilitate starting the engine and 
car. The centrifugal force and road clearance 
are important in determining the diameter. 

Material and Construction 

Flywheels are generally made of cast iron, 
and are machined all over to balance them. 
They are mounted on the end of the crank¬ 
shaft on the face of a flange, and are held 
onto this flange with either bolts or studs, 
which are locked by safety wires or cotter 
pins. The flywheel usually has marks on the 
circumference such as: “D. C.” (Dead Center), 
“E, O.” (Exhaust Opening), “E. C.” (Exhaust 


Closing), “1. O.” (Inlet Opening), and “I. C.” 
(Inlet Closing). 

When bolting the flywheel onto the crank¬ 
shaft, care should be taken that the marks 
line up properly with the crankshaft, because 
this flange may have four, six, or eight holes in 
it. This allows four, six, or eight different 
positions for the flywheel, consequently the 
marks on the flywheel may not line up with 
the crankshaft, causing a great deal of trouble 
when timing the camshaft. Care' should be 
taken when bolting the flywheel to the crank¬ 
shaft that no dirt rests between the surfaces, 
otherwise the flywheel will wobble and vibrate 
causing the bearings to wear. Some flywheels 
are keyed to the tapered end of the crankshaft, 
but this method of fastening is not as success¬ 
ful on account of the small diameter of the 
shaft, allowing the flywheel to continuously 
work loose and pound. 

The flywheel is also used as the clutch 
mounting for either the cone clutch or the disc 
clutch. The flywheel may have gear teeth 
machined on the circumference for the electric 
starter, or may have a steel gear pressed on it 
for the same purpose. 

VALVE TIMING, T-HEAD ENGINE 

As the T-head engine has two camshafts 
it is necessary to time each shaft sepa¬ 
rately. Time the exhaust camshaft first and 
then the inlet camshaft. Considering a single 
cylinder engine; with the tappets on the heel 
of the cam, adjust the exhaust valve clearance 
to .004" and the inlet valve to .002". Set 
the crankshaft 5° past T. D. C. Turn the 
exhaust camshaft in its direction of rotation 
until the exhaust valve just closes, which 
can be determined by placing a thin piece of 
paper between the end of the tappet and ex¬ 
haust valve stem and when the paper becomes 
free the valve is just seating. Lock the gear 
onto the camshaft, then turn the crankshaft 
forward about 5° and turn the inlet camshaft 
in its direction of rotation until the inlet valve 
is just opening, then lock the inlet camshaft 
gear in place. 

This places the piston on the end of the 
exhaust stroke and the start of the intake. 

Valve Timing of Engine with Automatic 
Inlet Valves 

To time the camshaft of an engine with 
automatic inlet valves, it is only necessary to 
time the exhaust camshaft. With the crank¬ 
shaft or flywheel a few degrees past top dead 
center, turn the exhaust camshaft in its direc¬ 
tion of rotation until the exhaust valve just 
closes, mesh the gears and lock in place. 










FLYWHEELS — VALVE TIMING 


41 


To Determine the Inlet from the Exhaust Valve 
by Their Movement 

Referring back to the valve openings and 
closings: The inlet valve opened just as the 
exhaust valve closed, or within a few degrees 
crankshaft travel from that point, while when 
the exhaust valve opened, the inlet valve did 
not close at that point. Turn the engine over 
and watch the action of the valves. When 
one valve closes and the other valve opens at 
the same time or immediately after, the one 
that closes is the exhaust, and the one that 
opens is the inlet. 

To Determine the Firing Point 

Open the priming cup or remove the spark 
plug; turn the engine over until compression 


is felt in the cylinder, then put a wire on the 
top of the piston and turn the crankshaft over 
until the piston reaches top dead center. This 
will be T. D. C. compression or firing point. 
Another method of setting the piston on the 
firing point is to crank the engine over until 
the inlet valve just closes. The crankshaft is 
now about 145° from the firing point; open the 
priming cup and place a wire on the head of 
the piston, turn the flywheel over until the 
piston reaches top dead center, or the “T. 
D. C.” mark on the flywheel lines up with the 
indicator, thus putting it on the firing point. 

CYLINDER CASTINGS AS USED ON 
MULTIPLE CYLINDER ENGINE 

Cylinders may be cast separately, or in pairs. 




MARKS 


D. C. Dead center. 

E. O. Exhaust opens. 
E.C. Exhaust closes. 


I.C. Inlet closes. 
1.0. Inlet opens. 
















































42 


ENGINES 


or there may be four cylinders cast in block, 
separate from the crankcase, but fastened to 
same with studs, having a paper gasket be¬ 
tween. In some constructions the cylinder 
block may have the upper half of the crank¬ 
case cast integral, eliminating the gasket and 
the machining of these surfaces. Where the 
cylinders are separate there are numerous 
joints and fittings to make the connections be¬ 
tween the various cylinders which necessitates 
extra machining on both the fittings and the 
cylinders. 

GENERAL PRINCIPLES OF OPERATION, 
MULTIPLE CYLINDER ENGINES 

In any four stroke cycle engine, after ,a 
certain cylinder fires, that same cylinder will 
not fire again until the crankshaft completes 
two revolutions, or 720°. After firing, the 
piston must perform a cycle of operations; 
consisting of Power, Exhaust, Intake and Com¬ 
pression strokes. 

On any four stroke cycle engine regardless 
of the number of cylinders, all cylinders will 
fire during two revolutions of the crankshaft, 
or 720°. 

There are three things that determine the 
distance apart of the explosions in a multiple 
cylinder engine; — the angle between the 
cranks, the angle between the cylinders, and 
the number of cylinders. 

In automobile engines if the cylinders and 
crank throws are set standard, the explosions 
will occur uniformly, or at regular intervals. In 
order to find the distance apart the explosions 
occur, divide 720° by the number of cylinders. 
A four cylinder engine will fire every 180°; a 
six, every 120°; an eight, every 90°; and a 
twelve, every 60°. 

When speaking of No. 1 spark plug, it refers 
to the spark plug in No. 1 cylinder; No. 4 ex¬ 
haust valve, the exhaust valve in No. 4 cylinder, 
etc. Consider the firing point as being T. D. C. 
compression. Firing point retard may be any¬ 
where from T. D. C. to 10° past, while the 
firing point in advance may be anywhere 
from 25° before T. D. C. to T. D. C. This will 
vary more or less on different engines. In 
automobile engines two pistons move together 
and will be 360° apart in operation. For 
example: In a four cylinder engine No. 1 and 
No. 4 move together, that is, when No. 1 is on 
T. D. C., No. 4 will be there also. If No. 1 was 
on T. D. C. compression (firing point) No. 4 
would be on T. D. C. exhaust—360° from the 
firing point. When the explosion occurs, No. 1 
will start moving down on Power stroke. Since 
there are only two different operations per¬ 
formed on the downward movement of the 


piston^—Power and Intake—and since both 
pistons do not perform the same operation at 
the same time. No. 4 would be moving down 
on intake. When two pistons are considered 
that move together it is found that if their 
crankshaft throws are anywhere from 10° past 
‘to 135° past T. D. C., one will be on Power, the 
other on Intake. When the crankshaft throws 
are between 45° before and 35° past B. D. C., 
one will be on exhaust, the other on intake. 
When the crank throws are between 35° past 
B. D. C. and T. D. C., one will be on compres¬ 
sion and the other on exhaust. When one fires, 
the other will be on exhaust. When the inlet 
valve opens in one the other will be on Power. 
When the exhaust valve opens in one the 
inlet will be open on the other. When the inlet 
valve closes in one, the other will be on ex¬ 
haust. When the exhaust valve closes in one 
the other will be on Power. 

Based on the average valve settings, as 
shown in Fig. 30, the duration of the strokes 
will be: 


Intake. 205° 

Compression. 145° 

Power . 135° 

Exhaust. 230° 

Lap . 5° 


Total. 720° 


When timing the ignition, always time from 
T. D. C. flywheel mark, or piston position,—not 
by the valve closings, as they vary on almost 
every engine. 

Timing the Valves Or Setting the Camshaft 

The valves may be timed by either fiywheel 
marks or piston position, and timed to the 
opening or closing of either the inlet or the 
exhaust valve in any cylinder. Timing by the 
fiywheel marks is preferable, because that will 
give the exact timing for that individual en¬ 
gine, provided the fiywheel marks are correctly 
located. 

Care must be taken when timing any cam¬ 
shaft that the camshaft and crankshaft are 
turned in the same direction that they revolve 
when the engine is running. 

Checking the Flyivheel Marks 

If the fiywheel marks are correct, when two 
pistons reach T. D. C. their relative mark 
should line up with the indicator. For example: 
when No. 1 and No. 4 pistons are on T. D. C., 
the fiywheel mark “D. C. 1-4” should line up 
with the indicator. 











M U L T I P LE CYLINDER ENGINES 


Establishing An Indicator 

Where there is no indicator stamped or fast¬ 
ened on the crankcase, one can be established 
by cranking the engine over until two pistons 
reach T. D. C. If Nos. 1 and 4 are taken, then 
place a mark on the crankcase that will point 
to, or be in line with “D. C. 1-4” mark on the 
flywheel. 

ESTABLISHING FLYWHEEL MARKS 

Where the flywheel is not marked, the tim¬ 
ing marks may be established provided the 
valve openings and closings are known. If the 


43 

flywheel has a circumference of 36 inches, it 
can be divided into 360 equal spaces and one 
inch will represent 10°;*one half inch, 5°, etc. 

Consider a four cylinder engine for example. 
Crank the engine over until Nos. 1 and 4 pis¬ 
tons reach T. D. C., then place a mark on the 
flywheel in line with the indicator. This mark 
will represent dead center for Nos. 1 and 4 ‘‘D. 
C. 1-4.” That is, any time that mark lines up 
with the indicator. Nos. 1 and 4 pistons will be 
at their highest point of travel. 

Turn the flywheel 5° farther in its direction 
of rotation and place a mark on the flywheel 



FIG. 32 

FOUR CYLINDER ENGINE (END VIEW) 










44 


ENGINES 


in line with the indicator. This will represent 
exhaust closing, Nos. 1 and 4 “E. C. 1-4.” 
That is, when that mark lines up with the indi¬ 
cator, Nos. 1 and 4 pistons will be in the cor¬ 
rect position for the exhaust valve to close. 
Turn the flywheel another 5° in its direction of 
rotation and place a mark on it in line with the 
indicator. This will represent the inlet valve 
opening position (10° past T. D. C.). That is, 
when the mark ‘T. O. 1-4” lines up with the 
indicator, Nos. 1 and 4 pistons will be in the 
correct position for the inlet valve to open. 

CRANKSHAFTS FOR TWO CYLINDER 
FOUR STROKE CYCLE ENGINES 

The crankshaft may have either two or three 
main bearings depending upon the general 
construction. The crank pins may be set op¬ 
posite one another, 180° apart, or both crank 
pins may be in the same plane, that is both 
together. The arrangements of these crank 
pins and the setting of the cylinders determine 


CRANKSHAFTS 


1-CYL. 


2-CYL. 




TWO CYLINDER COUNTER BALANCED 


FIG. 33 


the distance apart the cylinders fire in crank¬ 
shaft travel. The two cylinder engine is built 
in two types, one where both cylinders are in 
the same plane, and the other, the opposed 
type. In the opposed type the cylinders are set 
opposite one another. Motorcycle engines 
have the cylinders set about 221 / 2 ° from a ver¬ 
tical line, causing them to fire unevenly. 

Consider a two cylinder vertical engine, 
using a crankshaft with the crank throws set 
180° apart. It requires 720° crankshaft travel 
to perform the cycle of operations. Both cylin¬ 
ders should fire in two revolutions of the 
crankshaft. In this type of engine when num¬ 
ber one piston is on top dead center compres¬ 
sion or firing point, number two piston will be 
on bottom dead center, hence, the crankshaft 
must turn 180° before number two piston 


reaches the firing point. When number two 
fires, number one is on bottom dead center on 
the exhaust stroke, having completed 180° of 
its travel. Number one swings 180° to top 
dead center, just completing the exhaust 
stroke, necessitating another complete revolu¬ 
tion, or 360°, before it is ready to fire. So 
after number two cylinder has fired number 
one piston will travel 540° before it is ready 
to fire again. Number one and number two 
cylinders fired 180° apart, and number two and 
number one fired 540° apart, giving the full 
720° travel. A two cylinder engine of this de¬ 
sign is not very practical, causing considerable 
vibration through the variable firing. This 
vibration causes pounding on the bearings and 
general wear, besides general vibration in the 
installation. 

Consider the crankshaft again where the 
crank throws are set 180° apart in an op¬ 
posed engine. On this engine both pistons are 
on top dead center at the same time. On a 
two cylinder engine, in order to have the ex¬ 
plosions occur at equal intervals, an explosion 
must occur every 360°. Considering the right 
hand cylinder as firing, the left hand cylinder 
is on top dead center at the end of the exhaust 
stroke, 360° from its firing point. In the next 
360° travel, number two or the left hand cylin¬ 
der will be firing and number one will be at the 
end of the exhaust stroke, just 360° from its 
firing point. An engine of this type is evenly 
balanced, because the explosions occur at equal 
intervals. 

Consider the two cylinder vertical engine 
with both crank throws in the same plane. 
When number one is on top dead center, firing 
point, number two is also on top dead center, 
but at the end of the exhaust stroke. If num¬ 
ber one is firing, then 360° later, crankshaft 
travel, number two will fire, number one will 
be at the end of the exhaust stroke. The ex¬ 
plosions occur every 360°, or at equal intervals. 

The two cylinder engine is used mostly on 
marine, tractor, or stationary work. 

Timing Camshaft on Two Cylinder Elngine 

To time the camshaft on any multiple cyl¬ 
inder engine, it is only necessary to time the 
cams to one cylinder; the remaining cams are 
automatically timed as they are on the same 
camshaft. The shape of the crankshaft, the 
placing of cylinders and the way the camshaft 
is made determines the firing order. 

For instance, consider the two cylinder en¬ 
gine with both crank throws on top dead center 
at the same time. Every 360° crankshaft 
travel an exhaust valve will open, but as the 
camshaft travel is one-half as fast as the 
crankshaft, the exhaust cams will be placed on 














































45 


TWO C Y L I N DER ENGINE 


the shaft 180° apart and the same with the in¬ 
let cams. 

To time the camshaft on a two cylinder en¬ 
gine, adjust exhaust valve tappet to .004" 
clearance, turn the flywheel until the indicator 
lines up with the “E. C.” mark. The crank pins 
are now a few degrees past top dead center. 
Turn the camshaft in its direction of rotation 
until number one exhaust valve just closes, 
then mesh the gears and lock them in place. 

If it is an L-head engine with the valves on 
the same side, the inlet will be timed. If it is a 
T-head engine, after timing the exhaust valve 


—130° 

720 - ; 

t-* -230^ _ — ^ 

5° 



-- 

"^46 

P 

E 

I 

c 

— 180 ^ 

1 ONE CYL. 

p 

1 

1 

I E 

1 

I 

c 

c 

UJ 

CL 

I 

TWO CYL. 


1 


P 

1 

1 

E : 

I 

I 

c 

I c 

P E 


POWER CHART 


FIG. 34 

it will be necessary to turn the crankshaft for¬ 
ward a few degrees, then turn the inlet cam¬ 
shaft in its direction of rotation until number 
one inlet valve just starts to open. Mesh the 
gears and lock in place. Number one is on the 
end of the exhaust stroke, starting on the in¬ 
take, and number two will now be on the firing 
point, if the spark is fully retarded. 

To set number one on the firing point for 
timing the ignition, crank the engine over until 
number one inlet valve just closes. Open the 
priming cup, place a wire on the head of the 
piston, then crank the engine over in its direc¬ 
tion of rotation about three-eighths of a turn or 
until the wire reaches the highest point of its 
travel. Number one is now on the firing point 
in full retard. 

Setting by Compression: Crank the engine 
over until compression is felt in number one 
cylinder. Place a wire on the top of the piston. 


crank it over until the piston reaches top dead 
center, and number one will be on the firing 
point, in full retard. 

To Determine Which Cylinder Is Misfiring 

The pet cock on the engine can be opened 
and the sound of the explosion heard or the 
flame can be seen. When the engine has no pet 
cocks, other methods must be used. The 
temperature of the spark plug when the engine 
is stopped may be used to determine this. An¬ 
other method is, when the engine is running, 
take a screw driver, rest it on the cylinder and 
lean it over on the spark plug. This is what is 
termed shorting, or short circuiting the spark 
plug, giving a path of less resistance for the 
current than through the spark plug. Short 
circuiting a plug in a cylinder that is firing will 
slow down the speed of the engine. The engine 
will slow down and speed up as you move the 
screw driver back and forth onto a firing plug. 
When a plug is shorted in a cylinder that is 
not firing, it makes no difference in the running 
of the engine because that cylinder is dead. 

THREE CYLINDER FOUR STROKE CYCLE 
ENGINES 

The crank pins are spaced 120° apart. As 
the first cylinder that fires must be ready to 
fire again in the next 720° travel and it being 
necessary to have the explosions occur at equal 
intervals, the cylinders will fire every 240°, giv¬ 
ing three power impulses every 720° crank¬ 
shaft travel. This engine is used in marine 
work, but is no longer applied to automobiles. 

FOUR CYLINDER FOUR STROKE CYCLE 
ENGINES 

The crank pins are spaced 180° apart, hav¬ 
ing Nos. 1 and 4 crank pins in line and 
Nos. 2 and 3 in line, but 180° from Nos. 1-4. 
The number of main bearings on the crank¬ 
shafts in the four cylinder engine varies. It 
may be either a two, three or five bearing 
crankshaft. All four cylinder crankshafts have 
the crank pins spaced exactly the same; the 
only differences are in the arrangement and 
number of main bearings. The less the num¬ 
ber of main bearings, the more the crankshaft 
will spring and the heavier it must be. 

A four cylinder engine of the T-head type 
has one exhaust camshaft and one inlet 
camshaft, each camshaft having four valve 
operating cams which are either forged in¬ 
tegral with the shaft or keyed on. The four 
cylinder F, L or I-head engine has all the 
cams on one shaft, inlet cams being usually 
a different shape from the exhaust cams. On 
a four cylinder engine in order to have all four 
cylinders fire in two complete revolutions of 

















































46 


ENGINES 


the crankshaft and to have them occur at 
equal intervals they must fire every 180°. 
When all four cylinders have fired, number one 
must be ready to fire again. Firing every 180° 
crankshaft travel, and as the camshaft travels 
one-half as fast as the crankshaft, the exhaust 
cams are placed 90° apart, and the inlet cams 
are placed 90° apart. The order in which they 
open and close the valves will determine the 
firing order. 

Consider a four cylinder engine, with Nos. 


1-4 pistons on T. D. C.; either one of these two 
could be fired, depending on the position of the 
cams. Consider that No. 1 is firing. When 
No. 1 is firing. Nos. 2 and 3 are on bottom 
dead center, so the crankshaft will swing 180°, 
bringing Nos. 2-3 up, and the last closing of 
the inlet valve will determine which one of 
these two cylinders will fire next. Consider 
that No. 2 came up on the compression stroke. 
If No. 2 followed No. 1 on the compression 
stroke the firing order will start 1-2. The 



^ FIG. 35 

FOUR CYLINDER ENGINE (SIDE VIEW) 





























FOUR CYLINDER ENGINE 


47 


crankshaft will swing another 180° having 
completed 360° of its travel, bringing Nos. 1-4 
up on top dead center. The last time they 
were on top dead center, No. 1 fired and is now 
on the end of the exhaust stroke, so No. 4 fires. 
This gives a firing order thus far of 1-2-4. The 
crankshaft swings another 180°, bringing Nos. 
2-3 up. The last time they were up. No. 2 fired 
and is now on the end of the exhaust stroke, so 
No. 3 fires. This gives a firing order of 1-2-4-3. 

Again, consider Nos. 1-4 on T. D. C. and No. 
1 firing. The crankshaft will turn 180°, bring¬ 
ing Nos. 2-3 up. If No. 3 came up on compres¬ 
sion, it follows No. 1 in firing. Turn the crank- 

4 CYL VERTICAL AND 8 CYL V TYPE 



FIG. 36 


shaft another 180° bringing Nos. 1-4 up, and 
as No. 1 fired the last time it will be on the end 
of exhaust stroke putting No. 4 on the firing 
point. Turn the crankshaft another 180°, 
bringing Nos. 2-3 up. No. 3 will be on the end 
of the exhaust stroke, putting No. 2 on the fir¬ 
ing point. So the firing order will be 1-3-4-2. 
These are the two standard four cylinder firing 
orders: 1-2-4-3; 1-3-4-2. 

One standard firing order has no advantage 
over the other, and considering either end of 
the engine as number one, it does not make 
any difference in the firing order. Either end 
could be considered number one. If it has a 
1-2-4-3 firing order, it will be the same from 
both ends. 

The standard method of numbering cylinders 
is from the cranking end. 

Determining the Firing Order by the Movement 
of the Valves 

Choose the inlet valves in No. 1 and No. 2 
cylinders. Crank the engine over until No. 1 
inlet valve just closes, then watch No. 2. If in 
the next half revolution of the flywheel. No. 2 
inlet valve closes, the firing order is 1-2-4-3. If 


No. 2 does not follow No. 1 , the firing order is 
1-3-4-2. It is only necessary to watch the clos¬ 
ing of the two inlet valves. 

Either the openings or closings could be fol¬ 
lowed but as the closing of the inlet valves 
determine the compression and the firing it is 
easily remembered. To determine the firing 
order by compression, open No. 1 and No. 2 pet 
cocks, or remove the spark plugs from Nos. 1 
and 2 cylinders; crank the engine over until 
compression is felt in No. 1 cylinder. Then 
place your hand over the opening in No. 2 
cylinder and if compression is felt in No. 2 
half a revolution or 180° after No. 1, the firing 


—18( 

’1 

-720“-- 

p 

E 

r 

c 

c 

P E 

1 

I 

I 

C 

P E 

E 

1 c 

P E 


FIG. 37 


FOUR CYLINDER POWER CHART 

order is 1-2-4-3. But if No. 2 does not follow 
No. 1 on compression in the next 180°, the fir¬ 
ing order is 1-3-4-2. 

Timing Camshaft on T-Head Four 
Cylinder Engine 

It is necessary to time to one cylinder only. 
Adjust No. 4 inlet and exhaust valves to 
.002" and .004" clearance respectively. Crank 
the engine over until the flywheel mark “E. C. 
1-4” lines up with the indicator. Then turn the 
exhaust camshaft in its direction of rotation 
until No. 4 exhaust valve just closes, then mesh 
the gears and lock in place. Turn the flywheel 
a few degrees until the mark ‘T. O. 1-4” lines 
up with the indicator. Then turn the inlet cam¬ 
shaft in its direction of rotation until No. 4 in¬ 
let valve just starts to open. Mesh the gears 
and lock in place. No. 4 is now on the end of 
the exhaust stroke and the beginning of the in¬ 
take, and No. 1 is approximately on the firing 
point. Care must be taken to turn the cam¬ 
shafts in their direction of rotation. If cam¬ 
shafts are driven from the crankshaft by a 
chain, the camshafts turn in the same direc¬ 
tion as the crankshaft, but if driven by a gear, 
they turn in the opposite direction, excepting 






















































































48 


ENGINES 


where there is an idler gear between the 
crankshaft and camshaft gears. 

Timing Camshaft on L, I, or F-Head Engine 

Adjust No. 4 exhaust valve to .004" clear¬ 
ance. Crank the engine over until Nos. 1-4 
crank throws are about 5° past top dead cen¬ 
ter, or the flywheel mark “E. C. 1-4” just lines 
up with the indicator, or until Nos. 1-4 pistons 
reach T. D. C. and just start down, not more 
than 1/32". Turn the camshaft in its direction 
of rotation until No. 4 exhaust valve just closes, 
then mesh the gears and lock in place. This 
brings the other valves into time with their 
respective pistons. The inlet cams are placed 
on the same shaft and necessitate no other 
timing. No. 4 is now on the end of the exhaust 
stroke and the beginning of intake, which 
be on the firing point, with retarded spark. 

Finding the firing order on the L-head 
engine is the same as on the T-head. 

To set No. 1 on the firing point, crank the 
engine over until No. 4 exhaust valve just 
closes, which puts No. 1 at the beginning of 
the power stroke. Another method is to crank 
the engine over until No. 1 inlet valve closes, 
then open the pet cock and put a wire down 
on the head of the piston and turn the engine 
over until No. 1 reaches T. D. C. It will then 
be on the firing point, with retarded spark. 

To determine which cylinder is misfiring 
when the engine is running, it can be tested by 
the pet cock, or the screw driver method 
^ (grounding or shorting out spark plugs). If, 
when one is shorted, a difference in the run¬ 
ning of the engine is noticed, a plug has been 
shorted in a live cylinder, but when there is no 


difference in the running of the engine, a plug 
has been shorted in a cylinder that was not 
firing. 

SIX CYLINDER ENGINE CRANKSHAFTS 

A six cylinder crankshaft may have either 
three, five or seven main bearings. The more 
bearings there are the more rigidly the crank¬ 
shaft is held, the less wearing of the bearings 
and the less danger of breaking. The crank¬ 
shaft is so constructed that Nos. 1 and 6 crank 
pins are in line. Nos. 2 and 5 are in line, and 
Nos. 3 and 4 are in line. These three groups 
of crank pins are spaced exactly 120° apart. 
When No. 1 piston is on top dead center. No. 6 
will be in the same position, then Nos. 2 and 5 
come up together, followed by Nos. 3 and 4. 
Turning the crankshaft in one direction of ro¬ 
tation, it is noticeable that after Nos. 1-6 have 
moved up. Nos. 2-5 will follow, then Nos. 3-4. 
Turn the crankshaft end for end and turn it in 
the same direction of rotation as before, then 
when Nos. 1-6 move up. Nos. 3-4 will follow, 
then Nos. 2-5. When the crankshaft is made 
with Nos. 2-5 following Nos. 1-6, it is called a 
right hand crankshaft. When Nos. 3-4 follow 
Nos. 1-6, it is called a left hand crankshaft. 
This will make a difference in the firing order, 
as well as the order in which the cams are 
placed on the camshaft. 

All six cylinders must Are in two revolutions 
of the crankshaft, so that after the first cylin¬ 
der has fired and made two complete revolu¬ 
tions it is ready to Are again. The explosions 
should occur at equal intervals, or as close to 
it as possible to reduce vibration, so to have all 
six explosions occur in two revolutions, they 
should occur 120° apart. 



4 BEARING TYPE 

FIG. 38 



















































SIX CYLINDER ENGINE 


49 


Six Cylinder Firing Orders 

There are eight possible firing orders for the 
six cylinder engine, but engineers have elim¬ 
inated six and have kept the two best firing 
orders from a vibration, balance and carbure- 
tion standpoint. The two standard firing 
orders are: 

1-5-3-6-2-4 

1-4-2-6-3-5 

The other six possible firing orders for the 
six cylinder engine are: 

1-4-5-6-3-2 

1-3-5-6-4-2 

1-3-2-6-4-5 

1-5-4-6-2-3 

1-2-4-6-5-3 

1-2-3-6-5-4 

In the six cylinder firing orders not standard, 
two pistons on one end of the engine follow 
one another in firing, and on some engines with 
certain type inlet manifolds it will cause en- 
richening of the mixture, through having on 


120 


720 ' 


1 


c 


FIG. 39 

SIX CYLINDER POWER CHART 


one end, two explosions 120° apart and then an 
interval of 360°, while with the two standard 
firing orders, if a divided inlet manifold is used, 
with one branch leading to each end of the 
engine, there will be a suction in each direction 
every 240°. 

Standard Six Cylinder Firing Orders 

Consider Nos. 1-6 on T. D. C., with Nos. 2-5 


following. No. 1 will fire and No. 6 is on 
the end of the exhaust stroke. The crank¬ 
shaft turns 120°, bringing Nos. 2-5 up, and No. 
5 will fire. The crankshaft turns another 120°, 
bringing Nos. 3-4 up. No. 3 being on the front 
of the center line of the engine, should fire 
next. When No. 3 is firing. No. 4 is on top 
dead center at the end of the exhaust stroke. 
Firing order thus far is 1-5-3. Crankshaft 
swings another 120°, bringing Nos. 1-6 up 
again. As No. 1 fired last time. No. 6 will 
fire this time. In another 120° Nos. 2-5 are 
up. No. 5 fired last time, so No. 2 will fire 
this time. In the next 120°, Nos. 3-4 are up. 
No. 3 fired last time, so No. 4 will fire this time. 
The firing order is: 

1-5-3-6-2-4 

This gives an explosion every 120°. The 
cams must be arranged in the same order. No. 
5 exhaust cam follows No. 1, and as the cam¬ 
shaft revolves one-half as fast as the crank¬ 
shaft and the explosions are 120° apart crank¬ 
shaft travel. Nos. 1-5 exhaust cams are 60° 
apart, then No. 3 is 60° from No. 5. The shape 
of the crankshaft on the six cylinder engine 
determines the opening and closing of the 
valves and the firing order. 

To find the firing order of a 6 cylinder en¬ 
gine, if it is not known, first select the inlet 



FIG. 40 

SECTIONAL END VIEW, SIX CYLINDER 
L-HEAD ENGINE 
































































































50 


engines 


valves in Nos. 1-4 cylinders, then crank the en¬ 
gine over until No. 1 inlet valve closes, and if 
No. 4 inlet valve closes 120° or 1/3 revolution 
later, the firing order is 1-4-2-6-3-5. If No. 4 
inlet valve does not close 120° after No. 1, 
the firing order is 1-5-3-6-2-4. Or, if compres¬ 
sion is felt in No. 4 120° after it is felt in No. 
1 the firing order is 1-4-2-6-3-5. If not, the 
firing order is 1-5-3-6-2-4. Or, crank the en¬ 
gine over until No. 1 piston reaches T. D. C. If 
No 2 piston moves to T. D. C. 120° later, the 
firing order is 1-5-3-6-2-4. If not, it is 1-4- 
2-6-3-5. 

Timing Camshafts on Six Cylinder 
T-Head Engines 

Adjust No 6 exhaust valve to .004" clearance 
and No. 6 inlet valve to .002" clearance. 
Crank the engine over until the fiywheel mark 
“E. C. 1-6" lines up with the indicator, assum¬ 
ing that the fiywheel is fastened onto the 
crankshaft correctly, then turn the exhaust 
camshaft in its direction of rotation until No. 6 
exhaust valve just closes. Mesh the gears and 
lock in place. Turn the fiywheel a few de¬ 
grees until the mark ‘T. O. 1-6" lines up with 
the indicator. Turn the inlet camshaft in 


its direction of rotation until No. 6 inlet 
valve just starts to open, then mesh the 
gears and lock in place. No. 6 is now on the 
end of the exhaust stroke and beginning the 
intake; No. 1 is on the firing point. Or, crank 
the engine over until Nos. 1-6 pistons reach T. 
D. C. and move down not more than 1/32". 
Turn the exhaust camshaft in its direction 
of rotation until No. 6 exhaust valve just 
closes. Mesh the gears and lock. Turn the 
flywheel a few degrees in its direction of rota¬ 
tion, then turn the inlet camshaft in its direc¬ 
tion of rotation until No. 6 inlet valve just 
starts to open. Mesh the gears and lock in 
place. 

To put No. 1 on the firing point on the six 
cylinder engine, crank the engine over until 
No. 6 exhaust valve just closes. Then No. 1 
will be just a few degrees past T. D. C. on the 
firing point. No. 1 can be set on the firing 
point, by observing the inlet valve closing, then 
by placing a wire on the head of the piston and 
cranking the engine over until the piston 
reaches T. D. C. or the wire reaches the 
highest point of its travel, or until the flywheel 
mark “1-6 D. C.” lines up with the indicator. 



FIG. 41 

CUT OPEN SIDE VIEW OF L-HEAD ENGINE 




















EIGHT CYLINDER ENGINE 


51 


Timing Camshaft on Six Cylinder L, I or 
F-Head Engines 

Adjust No. 6 exhaust valve to .004" clear¬ 
ance. Crank the engine over until the flywheel 
mark “1-6 E. C.” lines up with the indicator, 
or until Nos. 1-6 pistons reach T. D. C. and 
move down not more than 1/32". Turn the 
camshaft in its direction of rotation until No. 
6 exhaust valve just closes, then mesh the gears 
and lock. 

The firing order can be found the same on 
this type of engine as on the T-head engine, 
by watching either the opening or closing of 
the valves. To set No. 1 on the firing point: 
After the inlet valve in No. 1 seats, bring 
the piston to T. D. C., or bring the flywheel 
mark “1-6 D. C.” in line with the indicator. By 
watching the inlet valve on No. 1 until it closes, 
it is positive that No. 1 is just going up on com¬ 
pression, so that when the flywheel mark “1-6 
D. C.” lines up with the indicator. No. 6 is 
on the end of the exhaust stroke and No. 1 is 
on the end of the compression stroke just 
ready to fire. 

EIGHT CYLINDER V TYPE ENGINE 
CRANKSHAFT 

The crankshaft used in the eight cylinder 
V' type engine is of the same design as in the 
four cylinder, with the crank throws set 180° 


*90^ 

- r20“ -> 

P 

E 

I 

C 

c 

p 

E 

I 

C 


C 

P 

E 

I 

I 

C 

P 

E 

I 

I 

C 

P 

E 

E 

I 

C 

P 

E 

E 

I 

C 

P 

E 

P 

E 

1 

1 

C 

P 


FIG. 42 

EIGHT CYLINDER POWER CHART 


apart. There are only four crank throws on 
this crankshaft. Nos. 1-4 are in line, as are 
also Nos. 2-3. On eight cylinder engines all 
eight explosions occur in two revolutions of 
the crankshaft, thus the explosions are 90° 


apart, for even firing. There are some engines 
made that do not fire every 90°. This 
may cause increased vibration at low speed, 
depending upon the number of degrees that 
the explosions vary from 90°. The cylin¬ 
ders are arranged in V shape, that is, four 
cylinders on each side, the V being at an 
angle of 90°, which brings a crank throw up 
every 90°, first in the right hand block and 
then in the left hand block. No. 1 cylinder is 
at the cranking end. The right cylinder block 
is on the right side and the left cylinder block 
is on the left side when viewed from the oper¬ 
ator’s seat. In no V type engines do two cylin¬ 
ders fire in the same block in succession. It 
fires first in one block and then in the other 
block. Consider the crankshaft turning over 
from the right hand block to the left hand 
block. There will be a cylinder firing in 
the left hand block every 180°, crankshaft 
travel, likewise in the right hand block. Thus 
when the explosions alternate from one to the 
other, they occur at 90° intervals. If the igni¬ 
tion was cut off on either the right or left hand 
block, the engine would run as a four cylinder 
engine, firing every 180°. There are four eight 
cylinder firing orders, any one of which may 
be used on V type engines. 

Consider Nos. 1R-4R as being up on top 
dead center. IR fires, and the crankshaft 
swinging 90° brings IL and 4L on T. D. C. 
Either one could be fired, but to prevent exces¬ 
sive vibration of the engine, it is preferable to 
fire them diagonally across to the opposite 
end. That would bring 4L on the firing point; 
the firing order thus far is 1R-4L. Then the 
crankshaft swings 90° farther, bringing 2R 
and 3R up. Either of the four cylinder firing 
orders may be employed, 1-2-4-3 or 1-3-4-2, so 
consider 2R to fire next. Crankshaft swings 
another 90° and brings 2L and 3L on top. 
The second one from the rear fires as 4L 
fired first, that will make 3L fire after 2R. 
Then the crankshaft swings another 90°, IR 
and 4R are on T. D. C. the second time, and as 
IR fired the last time 4R fires this time. 
The crankshaft swings another 90° and IL 
and 4L are on T. D. C., and as 4L fired the 
last time IL must fire now. Another 90° brings 
2R and 3R up. 3R is on the firing point as 
2R fired the last time, and is now on the ex¬ 
haust stroke. The crankshaft travels another 
90° and 2L and 3L are on top. 2L is on the 
firing point, because 3L is just finishing up the 
exhaust stroke. This gives a firing order of: 

1R-4L-2R-3L-4R-1 L-3R-2L 
The other eight cylinder firing orders are, as 
follows: 

1R-4L-3R-2L-4R-1L-2R-3L 
1R-1L-2R-2L-4R-4L-3R-3L 
1R-1L-3R-3L-4R-4L-2R-2L 





















































52 


ENGINES 


The last two are seldom used in automo¬ 
bile engines, but are used in some aircraft en¬ 
gines. They have a tendency to cause more or 
less vibration. By firing from one end of the 
engine to the other prevents the swaying 
vibration. 

To Find the Firing Order 

To find the firing order of an eight cylinder 
V type engine by observing the closing of the 
inlet valves, first watch IR inlet valve close, 
then in the next 90° crankshaft travel, 4L in¬ 


let valve should close. If it does not IL will 
follow IR. Consider that 4L does follow IR. 
Then in the next 90° crankshaft travel 2R inlet 
should close. If it does, the firing order will 
begin 1R-4L-2R, but if 2R does not follow 4L, 
3R will, and the firing order begins 1R-4L-3R. 
It is only necessary on the eight cylinder V 
type engine to determine the first three valve 
closings, because the second one determines 
whether the engine fires directly across or 
diagonally. The third one determines whether 
it has a 1-2 firing order, or a 1-3 firing order. 



FIG. 43 

EIGHT CYLINDER V TYPE ENGINE 


A. Crankshaft main bearing. 

B. 1-4 Crank pins. 

C. 2-3 Crank pins. 

D. 2-3 R. Connecting rods. 

E. 1-4 R. Connecting rods. 

F. 1-4 L. Connecting rods. 

G. 2-3 L. Connecting rods. 

H. 1-2-3-4 L. Pistons. 


I. 1-4 R. Pistons. 

J. 2-3 R. Pistons. 

K. Camshaft. 

L. Camshaft bearing. 

M. Rocker arm. 

N. Crankcase. 

O. Oil pan. 

P. Cylinder. 

Q. Water jacket. 


R. Cylinder head. 

S. Cylinder head gasket 

T. Combustion chamber. 

U. Exhaust manifold. 

V. Inlet manifold. 

W. Throttle arm. 

X. Carburetor. 

Y. Valve cover plate. 
























EIGHT CYLINDER ENGINE 


53 


The firing order can also be found by the com¬ 
pression method and as it is understood that 
the closing of the inlet valve determines the 
compression stroke, either method can be used. 
The compression method is necessary though 
on the sleeve valve engines since the valves 
cannot be seen. 

Timing Camshaft on Eight Cylinder 
V Type Engines 

Adjust No. 4R exhaust valve to .004" clear¬ 
ance. Crank the engine over until the flywheel 
mark “E. C. 1R-4R,” lines up with the indica¬ 
tor, or until 1R-4R pistons reach T. D. C. and 
move down not more than 1/32". Turn the 
camshaft in its direction of rotation until No. 
4R exhaust valve just seats. No. IR is on the 
firing point. No. IR can be put on the firing 
point also by watching for the closing of 
the inlet valve, then crank the engine over 
until the flywheel mark “D. C. 1R-4R” lines up 
with the indicator. As the explosions occur 
90° apart, the camshaft traveling one-half 


crankshaft speed, the exhaust cams are spaced 
45° apart, and the inlet cams the same, thus 
opening the valves 45° apart camshaft travel 
or 90° apart crankshaft travel. 

Some eight cylinder V type engines have 
sixteen cams, or one inlet cam for each inlet 
valve, and one exhaust cam for each exhaust 
valve, while some are built with the camshaft 
having only eight cams, four exhaust and four 
inlet. In the latter type, each cam operates a 
valve on both the right and left hand blocks, 
necessitating a special rocker arm arrange¬ 
ment in the crankcase. (See Fig. 45.) 

To Test for a Misfiring Cylinder 

On eight or twelve cylinder V type engines, 
it is necessary to cut off one block entirely 
to test for misfiring. Then find the misfiring 
cylinder by the screw driver method. If upon 
cutting off one block it is noticed that the block 
that is running is firing in all four cylinders, 
disconnect this one and connect the other, try¬ 
ing each cylinder separately to find which one 





EIGHT CYLINDER V TYPE ENGINE 
FIRING ORDERS 


A. 

B. 


1R—1 Lf—2 R—2 L—4 R—4 L—3 R—3 L. 
IR—IL—3R—3L—4R—4L—2R—2L. 


C. 

D. 


IR—4L—2R—3L—4R—IL—3R—2L. 
IR—4Lr-3R—2L—4R—1L^2R—3L. 











54 


ENGINES 


is misfiring. This is necessary because of the 
short lap between the explosions. 

EIGHT CYLINDER VERTICAL ENGINE 

In the eight cylinder vertical engine the 
cylinders are set in line, and its principles of 
operation are the same as if there were two 
four cylinder engines placed together end to 
end, with the crankshafts coupled so that the 
throws form right angles, or in such a manner 
that 90° after Nos. 1-4 reach T. D. C. in one 
half of the engine Nos. 1-4 in the other half of 
the engine will be on T. D. C. The same stand¬ 
ard four cylinder firing order is used in each 
half of the engine with the explosions alter¬ 
nating from one end to the other. 

In the eight cylinder vertical engines, the 


cylinders are numbered 1-2-3-, etc., from 
the cranking end, the same as in the other 
vertical engines. The crank throws are set 90° 
apart so that every 90° two pistons will reach 
T. D. C, This gives an explosion every 90°, 
with all cylinders firing in 720°. Nos. 1-4 
pistons move together, also Nos. 2-3, the same 
as in a four cylinder engine. Nos. 5-8 move 
together and Nos. 6-7. 

Firing Orders 

The two most probable firing orders are: 

1-5-2-6-4-8-3-7 

1-5-3-7-4-8-2-6 

To find the firing order, watch the order of 
valve closings, or the order of compression. 



FIG. 45 

ROCKER ARM ARRANGEMENT, EIGHT CYLINDER 
V TYPE ENGINE WITH EIGHT CAMS 


A. Rocker arm. 

B. Tappet. 


C. Camshaft. 

D. Roller. 













































TWELVE CYLINDER ENGINE 


55 


Timing 

In timing the valves, use the same method 
as in any other engine. Crank the engine over 
until the flywheel mark “E. C. 1-4” lines up 
with the indicator, or until Nos. 1-4 pistons 
reach T. D. C. and move down not more than 
1/32”. Turn the camshaft in its direction of 
rotation until No. 4 exhaust valve just closes. 
Mesh the gears and lock in place. 

TWELVE CYLINDER V TYPE ENGINE 

The crankshaft used in this engine is the 
same as the six cylinder crankshaft, excepting 
that the crank pin bearings are somewhat 
longer. There may be, either a three, five or 
seven bearing crankshaft in the twelve cyl¬ 
inder engine, depending upon the design of 
the engine. In the twelve cylinder engine, all 
twelve cylinders must fire in two revolutions. 



TWELVE CYLINDER POWER CHART 

SO to have the explosions occur at equal 
intervals it is necessary to have one ex¬ 
plosion every 60° crankshaft travel. On the 
V type engine where the explosions occur 
every 60°, the cylinders are placed at an 
angle of 60° on the crankcase, but there are 
some twelve cylinder engines that do not fire 
every 60°. For instance, the Libertv aircraft 
engine fires at unequal intervals of 75° and 45°. 
On this engine the cylinders are placed at an 
angle of 45°. As in the eight cylinder V type 
engine, where the four cylinder firing order is 
used in each block, the twelve cylinder engine 


using a six cylinder crankshaft has a standard 
six cylinder firing order in each block. The 
twelve cylinder V type engine fires either di¬ 
agonally or directly across. The firing orders 
are : 

1 R-6L-4R-3L-2R-5L.6R-1 L-3R-4L-5R-2L 

1 R-6L-5R-2L-3R-4L-6R-1 L-2R-5L-4R-3L 

1R-1L-4R-4L-2R-2L-6R-6L-3R-3L-5R-5L 

1R-1L-5R-5L-3R-3L-6R-6L-2R-2L-4R-4L 

The last two firing orders fire from the right 
to the left hand block directly across. This is 
seldom if ever found. In the first firing order 
given, when No. IR is on T. D. C., No. 6R is on 
T. D. C. at the same time, so when No. IR fires. 
No. 6R will be on the end of the exhaust stroke. 
Then the crankshaft swings over and brings 
No. IL and No. 6L on T, D. C., so it can fire 
either directly across from No. IR or diagonal- 
Iv, the latter of which is the most preferable. 
So No. 6L will follow No. IR. Then in the next 
60°, Nos. 3R and 4R will move up on T. D. C. 
No. 4R fires, then in the next 60°, Nos. 3L-4L 
reach T. D. C. and No. 3L will fire. Then in 
the next 60°, Nos. 2R-5R reaches T. D. C., so 
No. 2R will fire next. Swing the crankshaft 
another 60° and that will bring Nos. 2L-5L up, 
and No. 5L will fire next. In the next 60° Nos. 
1R-6R are up, and as No. 1-R fired the last 
time. No. 6R must fire. Then in another 60° 
No. 1L-6L are up. No. 6L fired the last time, 
so No. IL must fire. The next 60° of crank¬ 
shaft travel brings Nos. 3R-4R up, and No. 4R 
having fired the last time. No. 3R will fire this 
time. In the next 60° Nos. 3L-4L reach T. D. 
C., and as No. 3L fired last time. No. 4L will 
fire. In another 60° Nos. 2R-5R will reach 
T. D. C., and No. 2R firing last time. No. 5R 
will fire. Swing the shaft another 60° and 
Nos. 2L-5L will reach T. D. C. As No. 5L fired 
last. No. 2L will fire this time. This will give 
the firing order: 

1R-6L-4R-3L-2R-5L-6R-1L-3R-4L-5R-2L 

Timing Camshaft on Twelve Cylinder 
Sixty Degree V Type Engine 

Adjust No. 6R exhaust valve to .004” clear¬ 
ance. Crank the engine over until flywheel 
mark ‘‘E. C. 1R-6R” lines up with the indicator, 
or until Nos. 1R-6R pistons reach T. D. C. and 
move down not more than 1/32”. Turn the 
camshaft over in its direction of rotation until 
No. 6R exhaust valve just closes. Then mesh 
the gears or chain and lock in place. No. IR is 
now on firing point retard. No. IR can be 
set on the firing point by watching No. IR inlet 
valve close and then bring the piston to T. D. 
C. or the flywheel mark “1R-6R T. D. C.” in 
line with the indicator. 





























































56 


ENGINES 


To Find Firing Order of Twelve Cylinder 
V Type Engine 

Crank the engine over until No, IR inlet 
valve just closes. Then No. 6L inlet valve 
should close next, and if it does the firing order 
is diagonal, but if it does not, the firing order 
is directly across. Then in the next 60° of 
crankshaft travel No, 4R should close and if it 
does the firing order starts 1R-6L-4R, but if 


No. 4R does not follow No. 6L, the firing order 
is 1R-6L-5R, the same as in the six cylinder 
firing order. 

Crank the engine over until No. IR piston 
reaches T. D. C. If No. 2R piston moves to 
T. D. C. 120° or 1/3 revolution later, the firing 
order starts 1R-6L-5R. If No. 2R does not 
reach T. D. C. 120° after No. IR, the firing 
order starts 1R-6L-4R. 



FIG. 47 

TWELVE CYLINDER V TYPE ENGINE 


A. 

Camshaft. 

H. 

Exhaust manifold. 

0. 

Bevel drive gears. 

B. 

Camshaft hearing. 

I. 

Valve spring. 

P. 

Bevel driven gear. 

C. 

Camshaft housing. 

J. 

Inlet manifold. 

1. 

Clearance adjusting screw. 

D. 

Roller. 

K. 

Combustion chamber. 

2. 

Spacing shims. 

E. 

Rocker arm. 

L. 

Water jacket. 

3. 

Jam nut. 

F. 

Clearance. 

M. 

Vertical shaft housing. 

4. 

Lock nut. 

G. 

Valve stem guide. 

N. 

Vertical shaft. 

5. 

Clamping bolt. 
































































TWELVE CYLINDER ENGINES 


57 


To Find Which Cylinder Is Misfiring 

Cut off the ignition on one block, then short 
out the plugs one at a time until the cylinder 
that is misfiring is located. In shorting out a 
plug in a cylinder that is dead it will make no 
difference in the running of the engine, while if 
a plug is shorted in a cylinder that is firing it 
slows down the engine. 

Timing Camshaft on Twelve Cylinder 
Sixty Degree V Type Engine 
Overhead Czmnshafts 

To time the camshafts on engines using two 
overhead camshafts, crank the engine over 
until the flywheel mark “E. C. 1R-6R” lines up 
with the indicator. Have 6R and IL exhaust 
valves adjusted to .004" clearance. Turn the 
right hand camshaft in its direction of rotation, 
until No. 6R exhaust valve just closes, mesh 
the gears and lock in place. Turn the flywheel 
over in its direction of rotation about 60° or 
until flywheel mark “E. C. 1L-6L” lines up with 


the indicator. Then turn the left hand cam¬ 
shaft in its direction of rotation until No. 
IL exhaust valve just closes, then mesh the 
gears and lock in place. No. 6L is on firing 
point retard, and No. IR will be 60° past the 
firing point. On these engines it is necessary 
to know the firing orders to be able to time 
them properly. 

KNIGHT SLEEVE VALVE ENGINE 

In the Knight engine, the valve operating 
mechanism consists of thin cast iron sleeves 
placed within the cylinders. They control the 
port opening and closing, or strokes. This type 
of engine was invented by Charles Y. Knight, 
an American Engineer, who received very little 
encouragement from American manufacturers. 
European manufacturers, however, recognized 
the good features of this design and several 
prominent European cars use this type engine. 
It is now used in this country on models 
of Willys Knight, Stearns Knight, Handley 



R.B. LB. R.B. L.B. 

A B 


FIG. 48 

TWELVE CYLINDER V TYPE FIRING ORDERS 

A IR—6L—4R—3L—2R—5L—6R—IL—3R—4L/—5R 2L 
B. ir_6L—5R—2L—3R—4L—6R—IL—2R—5L—4R—3L 



I 


58 


ENGINES 



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KNIGHT SLEEVE VALVE ENGINE 


59 


Knight, and R. and V. Knight (formerly the 
Moline Knight), in units of 4, 6 and 8 cylinders. 

Operation 

The operating principles of this engine are 
practically the same as in any four stroke 
cycle engine, the only difference being in the 
method of admitting and exhausting the gases 
from the cylinder. The cylinders are usually 
cast in block. Near the top of each cylinder 
are two ports which are connected with the 
inlet and exhaust manifolds respectively. The 
cylinder is waterjacketed, and inside of this 
member and interposed between the cylin¬ 
der and piston are two thin cast iron 
sleeves, extending from the crankcase to 
the top of the combustion chamber. These 
sleeves are actuated or moved up and down by 
small connecting rods, which are driven by 
an eccentric shaft. The eccentric shaft is 
driven from the crankshaft by a silent chain 
or gears, at one-half crankshaft speed. 

The sleeves have large slots which line 
up with the openings or ports in the cylinder 
wall, allowing the gases to enter and exhaust 
at approximately the same time and in the 
same relation to the movement and position of 
the crankshaft and piston as in the poppet 
valve engine. The travel of the sleeves is com¬ 
paratively small, their velocity being about 
1/10 that of the piston. The openings in the 
sleeves are wide enough, so that the gases 
can enter and exhaust more quickly than in the 
poppet valve engine. These openings are not 
obstructed by a valve head which has a tend¬ 
ency to break up and retard the movement of 
the gases when entering and leaving the cyl¬ 
inder. 

Some of the advantages claimed by the man¬ 
ufacturers of this engine are: smooth running, 
quietness of operation especially at high 
speeds, greater flexibility, and the ability to re¬ 
tain its compression longer than the poppet 
type, because carbon forming on the surface 
of the sleeves improves the compression, while 
carbon forming on the face of poppet valves 
will prevent them from seating properly, re¬ 
sulting in a loss of compression. 

The sleeves are lubricated in the same man¬ 
ner as the piston and cylinder wall, by an oil 
vapor from the crankcase. To insure more 
equal distribution of the oil over the surface 
of the sleeves, oil holes and spiral oil grooves 
are provided. 

The action and operation of the sleeve valve 
engine is positive at all speeds. In the poppet 
valve engine, the tappet will not always follow 
the contour of the cam at high speed, hence, 
the action is sometimes erratic. 

The combustion chamber in a sleeve valve 
engine is one of the most efficient of any design 


used. The inside of the combustion chamber is 
machined accurately and smoothly. This gives 
uniform compression, and has less tendency 
for carbon deposit to form. It is an engine 
that improves with use. This is true only in 
this way; due to the great surface area of the 



SLEEVE VALVE ENGINE 

A. Cylinder head bolt. 

B. Cylinder head. 

C. Exhaust port. 

D. Inlet port. 

E. Removable water jacket. 

F. Nut. 

G. Water space. 

H. Piston. 

I. Connecting rod. 

J. Outer sleeve. 

K. Inner sleeve. 

L. Outer sleeve connecting rod. 

M. Eccentric shaft. 

N. Eccentric shaft mounting. 






















































60 


ENGINES 


sleeves, it is impossible to machine these ac¬ 
curately enough to hold the maximum com¬ 
pression. When these sleeves are new there 
is a tendency for the lubricating oil to work 
up through the uneven surface of the sleeves 
and the mixture will move down in the 
same way. But eventually, the high spots will 
wear down, and the lubricating oil and con¬ 
densed mixture collecting in the low spots will 
be burned by the heat from the combustion 
chamber, so that these sleeves will in time 
wear into a more even surface. 

Some of the disadvantages claimed by other 
manufacturers are; this type of engine due to 
its design is not s\iitable for racing engines, 
aircraft engines, tractors, etc., or for any pur¬ 
pose that demands a constant load at a wide 
open throttle. That is, if the sleeves are 
given clearance sufficient to hold the compres¬ 
sion when the engine is cold, at high speeds or 
at high temperature the sleeves will start 
scoring and cutting from expansion. If the 
sleeves are given enough clearance to pre¬ 
vent excessive friction at high speeds or tem¬ 
perature, the clearance will be so great when 
the engine is cold that it is impossible to hold 
maximum compression. But for automobile 
use, where the speed and load is variable, 
where a constant load and wide open throttle 
are not used to any great extent, the sleeve 
valve engine is very satisfactory. 

If the sleeves become worn they cannot be 
rebored, as they are too thin. It is necessary to 
replace with new sleeves and pistons of the 
original size. The new sleeves will, in time, 
wear in to the proper clearance. 

Finding Firing Orders 

To find the firing order of a sleeve valve en¬ 
gine, use the compression method. If it is a 
four cylinder engine, crank the engine over 
until compression is felt in No. 1 cylinder, and 
if compression is felt in No. 2, 180° or one- 
half a revolution later, the firing order is 1-2- 
4-3. If compression is not felt in No. 2, then 
the firing order is 1-3-4-2. 

Setting Eccentric Shaft 

If in a six cylinder engine, remove the spark 
plug and exhaust manifold from No. 6 cylinder, 
crank the engine over until the flywheel mark 
“E. C. 1-6” lines up with the indicator, or 
until Nos. 1-6 pistons reach T. D. C. and 
move down not more than 1/32". Place a 
light down in No. 6 spark plug hole. With¬ 
out moving the crankshaft, turn the eccentric 
shaft in its direction of rotation until the light 
that is seen through the open exhaust port is 
just shut off; at this point the exhaust port is 
closing. Mesh the gears or connect the chain 
around the sprockets. 


To Place No. 1 on Firing Point 

After feeling compression in No. 1 cylinder, 
turn the crankshaft until No. 1 piston reaches 
T. D. C. This will be T. D. C. compression, or 
the firing point. 

SPARK PLUGS 

The spark plugs are constructed of several 
different materials. The shell is usually made 
of steel, and has a thread cut on it for screwing 
into the cylinder; the threaded portion may be 
tapered to insure a tight fit in cylinder. The 
metric size seats on a copper and asbestos 
gasket; this plug is used mostly in foreign, 
aircraft, or motorcycle engines. The S. A. E. 
standard plug has a —18 thread base and 

seats on a copper and asbestos gasket to 
prevent leakage. The porcelain that is used 
in plugs is of a kind that will stand high 
pressure and high temperature without crack¬ 
ing. If the porcelain should be cracked, the 
spark will jump through the broken porcelain 
over to the shell instead of jumping the gap in 
the end of plug that is in the cylinder. The 
resistance of the gap at the end of the elec¬ 
trodes is greater under compression than it 
is under atmospheric pressure. Many of the 
plugs will fire at the points or gap when they 
are laid out in the open, but under compression 
the spark will jump through a slight crack in 
the porcelain. To test the plugs, increase the 
gap to about a quarter of an inch, then test, 
and if it will jump a quarter inch gap under 
atmospheric pressure, it will function properly 
under compression. The gap between the cen¬ 
ter electrode to which the wire is connected 
from the distributor, and the electrode which is 
fastened onto the shell, varies on different en¬ 
gines, depending upon the ignition system used. 
A clearance of approximately .025" to .030" 
will be sufficient on the average automobile 
engine. 

The porcelains may be held in the shell by a 
nut, with gaskets between to prevent leakage, 
or there may be part of the shell shoulder 
rolled down on top of the porcelain to prevent 
leakage. Where the nut is used the porcelain 
can be replaced. The spark plug should be 
kept clean by cleaning with kerosene and 
scraping out thoroughly. 

The spark plug is generally placed in the 
cylinder as close to the inlet valve as pos¬ 
sible, so that the inrushing gases will wash off 
the carbon and oil or whatever formation there 
may be on the electrodes. Where the hole 
that the spark plug fits into is very deep, the 
extension plug should be used, because of the 
burned gases that would stay in this pocket 
and prevent fresh gases from coming in con¬ 
tact with the electrodes, causing hard starting 




CRANKCASE 


61 


and misfiring. Some engines have double igni¬ 
tion systems, using two spark plugs in the 
cylinder placed at different points. This gives 
an increase in power. From the instant that 
the gases ignite until they are fully burning, 
there is a loss of time. Consequently, if there 
are two spark plugs to ignite the gases at 
different points in the cylinder and both ignit¬ 
ing at the same time, the gases will burn a 
great deal faster. Most aircraft engines use 
the double ignition for this reason and also as 
a precaution, so that if one plug fails, there is 
another in the cylinder to fire. Keep the spark 
plug points adjusted uniformly to prevent un¬ 
even explosions and vibration of the engine. 

Spark plugs are divided into two different 
types. One is the petticoat, or hollow type, 
where the center electrodes project through 
the hollow porcelain, not being imbedded in 
the end of it. The other is the conical type 
where the electrode extends through the 
porcelain about This conical type is 

preferable on high compression engines, be¬ 
cause the compression would have a tendency 
to heat the electrode too readily if it was ex¬ 
posed to the heat, causing pre-ignition. Some 
spark plugs have numerous points, or elec¬ 
trodes, but one is all that is necessary, be¬ 
cause the spark will only jump one gap and 
if one should become shorted it will prevent the 
others from working. So with two electrodes 
and as short as possible, the less trouble there 
will be. The electrode on the shell should be 
bent downward and then up, so any oil forming 
on it will run down onto the depression, keep¬ 
ing the oil away from the gap to prevent foul¬ 
ing. (See Fig. 245, Electrical section.) 

CRANKCASE 

Various materials are used in the construc¬ 
tion of crankcases, the most common of which 
are cast iron and aluminum. Some are made of 
bronze, but are not used in automobile con¬ 
struction. The purpose of the crankcase is for 
mounting the crankshaft, camshaft and cylin¬ 
ders, and enclosing the same with their bear¬ 
ings to allow for lubrication without loss of oil. 
The crankcase may be cast integral with the 
cylinders or may be separate. The oil pan is 
fastened to the bottom of the crankcase. The 
gear housing or gear casing is cast integral 
with the crankcase, requiring a cover to en¬ 
close the gears. This cover fastens onto the 
gear housing with bolts or screws with a thin 
paper or cork gasket between. Use shellac on 
one side of the gasket and graphite on the 
other to prevent injuring it when removing. 

The crankcase may have a breather tube, 
either cast integral with it or fastened separate. 
This breather tube serves as the oil filler tube 
providing a place to pour oil into the crank¬ 


case and has baffle plates within to prevent the 
oil from splashing out. There, must be an 
opening in the crankcase to allow the heat to 
pass out, otherwise the bearings may burn out 
through overheating and thinning down of the 
oil under the high temperature. As the pistons 
come down they have a tendency to force this 
hot vapor out. 

Crankcases may become cracked as a result 
of a connecting rod breaking, necessitating 
welding. When welding the crankcase, wheth¬ 
er aluminum or cast iron, it is necessary to pre¬ 
heat the casting to prevent further cracking 
and excessive warping. Notwithstanding these 
precautions, the casting may warp to a certain 
extent, necessitating remachining the cylin¬ 
der and oil pan surface, to prevent oil leakage. 
The crankcase may have mounted upon it the 
ignition drive bracket, starting motor bracket, 
or generator bracket. 

OIL PAN 

The oil pan may be a sheet steel stamping 
or a light aluminum casting. The purpose of 
this oil pan is to act as an oil reservoir and 
furnish a mounting for the oil pump and oil 
level indicator. It may have troughs into 
which the connecting rods splash. It is held to 
the crankcase proper by studs or cap screws, 
with a cork or felt gasket between the two 
surfaces to prevent oil leakage. The oil level 
indicator indicates the amount of oil that is in 
the reservoir. 

COOLING SYSTEMS 

The great heat developed within the com¬ 
bustion chamber, in addition to the heat of 
friction between the piston and cylinder, would 
cause the metals to bind or seize, the lubricat¬ 
ing oil to decompose, and possibly cause prema¬ 
ture explosions, if there was not some means 
provided for cooling the engine. At the 
same time, since the efficiency of the engine 
depends upon its ability to utilize the greatest 
number of heat units generated in the com¬ 
bustion chamber, it is evident the more heat 
units transferred to the cooling agent, the less 
the efficiency of the engine. Therefore the 
design and operation of the cooling system is 
very important. 

There are two types of cooling systems, one 
using a current of air circulating around the 
engine, and the other using a water jacket, 
the water being kept in circulation and cooled 
by exposure to cooler air currents. 

AIR COOLING SYSTEM 

Air cooled engine cylinders have the walls 
constructed somewhat lighter than on the 
water cooled type, for the purpose of radiating 



62 


ENGINES 



THERMO-SYPHON COOLING SYSTEM 
TYPICAL FAN MOUNTING 

The arrows indicate the water circulation. The 
water is caused to circulate by the difference between 
the temperature of the water in the water jackets and 
the water in the radiator. 


A. 

Fan mounting and 

belt adjustment. 

L. 

Fan belt drive pulley. 

B. 

Inner bearing. 


M. 

Cylinder block. 

C. 

Outer bearing. 


N. 

Water jacket. 

D. 

Oil plug. 


O. 

Water outlet manifold. 

E. 

Felt oil retaining 

washers. 

P. 

Upper hose connection. 

F. 

Fan belt. 


Q. 

Upper chamber. 

G. 

Fan hub. 


R. 

Lower chamber. 

H. 

Fan shaft. 


S. 

Drain cock. 

I. 

Adjusting nut. 


T. 

Radiator filler tube. 

J. 

Radiator. 


U. 

Hose clamps. 


K. Lower hose connection. 























































































































































cooling systems 


63 


the heat more rapidly. These cylinders have 
fins cast on their exterior to help dissipate the 
heat. The air cooled engine has higher thermal 
efficiency than the water cooled engine. Run¬ 
ning at a higher temperature, less heat is rad¬ 
iated or taken away from the combustion 
chamber. This reduces the loss by cooling 
and leaves more to be converted into power, 
and under normal conditions an air cooled en¬ 
gine will give good service. They are not very 
successful when used to produce maximum 
power continuously, as the fins will not radiate 
the heat fast enough. A fan is used to draw an 
air blast around the cylinders for proper cool¬ 
ing. Air cooled engines, because of the higher 
temperatures necessitate greater clearance on 
all bearing surfaces including valve stems, con¬ 
necting rods, crank pin bearings, tappets, etc. 

Due to the fact that the cylinder expands 
more than in the water cooled type less 
clearance will be required on the piston. 
On the old type aluminum alloy piston used in 
the Franklin, about .011" and .003" clearance 
was allowed. But on the new pistons that are 
being used at present (long type) only about 
.005" and .002" are allowed. This prevents 
any chance of a piston slap when the engine is 
cold, but will sometimes slap after the engine 
heats up to normal operating temperature. If 
the pistons are fitted tight enough to prevent 
slapping at high speeds they may seize at lower 
speeds. 

The general practice in fitting piston pins in 
this type engine is to heat the pistons by plac¬ 
ing them in hot oil, then fit the piston pins to 
a snug pressing, fit with the palm of the hand. 
If they are fitted when cold, as in a water cool¬ 
ed engine, a knock may develop, when the en¬ 
gine is hot. This will be caused by the pis¬ 
ton expanding more than the piston pin. 

WATER COOLING SYSTEM 

In the water cooling system a circulation of 
water through the water jacket and radiator 
is maintained to keep the cylinders cool. 
There are two types of water cooling systems, 
thermo-syphon and pump circulation. 

Thermo-Syphon Type 

With the thermo-syphon cooling system, 
there is no pump or other mechanical device 
to circulate the water through the engine and 
radiator. The thermo-syphon cooling system 
works on the principle of hot water being 
lighter than cold water, or by the difference 
in the weight of water at different temper¬ 
atures. Water at 39° F. temperature weighs 
62.4 lbs. per cubic foot, while water at a tem¬ 
perature of 212° F. weighs 59.8 lbs. per cubic 
foot. It is this difference in the weight of the 
water at different temperatures that causes the 


water to circulate through the system. As the 
engine heats up, the water in the water-jacket 
will be heated, the hot water will rise to the 
top and pass over into the radiator practically 
being forced by the cooler water entering the 
bottom of the water jacket from the bottom of 
the radiator. Air currents acting upon and 
passing through the radiator cool the water in 
^ it, causing the cooler water to settle to the 
‘ bottom of the radiator where it is ready to 
enter the water jacket again, thus making a 
constant circulation of water through the 
cooling system. 

This system does not cool high speed or 
heavy duty engines sufficiently, the water not 
passing through the radiator fast enough. On 
the thermo-syphon cooling system there will 
be no circulation of the water until there is a 
considerable difference between the tempera¬ 
ture of the water in the lower radiator cham¬ 
ber and the water in the jackets of the engine. 
The water inlet and outlet hose connections 
on the thermo-syphon system are considerably 
larger than on the pump circulating system 
and should be kept free at all times. 

Pump Circulation Type 

The type of pump that is used to circulate 
the water depends upon the type of the engine 
and its application. Marine engines of the 
smaller type use the plunger pump to circulate 
the water, while the larger marine engines use 
the gear pump. A pump of these types is 
necessary because the water must be drawn a 
considerable distance. 

On automobile engines the radiator be¬ 
ing about the same height as the engine, de¬ 
mands only a circulating pump. This circu¬ 
lating pump does not require any suction, 
being connected between the radiator and en¬ 
gine and using the impellers to force the water 
through. 

On this system, the instant the engine 
starts, the water begins to circulate, conse¬ 
quently it will take an engine with a cool¬ 
ing system of this type longer to heat up to its 
correct running condition than one with the 
thermo-syphon system. This system prevents 
the engine from overheating more than the 
thermo-syphon. The radiator is generally 
iconnected to the pump by hose, and there is 
an outlet hose from the top of the cylinder 
to the top of the radiator. If these hose con¬ 
nections become clogged in any manner, there 
is a tendency to stop some of the water from 
circulating and cooling, consequently causing 
overheating of the engine. 

Where the pump circulating system is em¬ 
ployed a method is sometimes provided to 
retard the circulation until the engine heats up. 
In some instances shutters are provided at 




64 


ENGINES 



CIRCULATING WATER COOLING SYSTEM 
THERMOSTATIC CONTROL 


A. Radiator tubes. 

B. Upper chamber. 

C. Lower chamber. 

D. Drain cock. 

E. Hose clamp. 

F. Hose. 

G. Water pump. 

H. Water inlet manifold. 


I. Water outlet manifold. 

J. Water jacket. 

K. Thermostat. 

L. Valve. 

M. Water by-pass. 

N. Fan. 

O. Grease cups. 

P. Fan belt. 


Q. Flexible coupling. 

R. Water pump shaft. 

S. Packing nut. 

T. Hose. 

U. Cylinder block. 

V. Oil pan. 

W. Drain plug. 

X. Gear case cover. 


The purpose of the thermostat in the cooling system 
is to regulate the flow of the water to the radiator so 
as to allow the engine to heat to the normal operating 
temperature as soon as possible and keep the water at 
approximately an even temperature. When the engine 
first starts and the water is cold, the water passes 
through the passage (M) back to the pump without 
haying passed through the radiator. The water con¬ 
tinues to circulate in this way until it reaches a pre¬ 
determined temperature. This temperature is sufficient 
to cause the thermostat (K) to expand and open the 
passage into the radiator. 


This passage remains open while the temperature 
of the water remains above that at which the thermo¬ 
stat operates. Should the temperature of the water 
decrease, the thermostat will contract, closing the pas¬ 
sage to the radiator, again allowing the water to heat. 

The use of the thermostat tends to increase the 
efficiency of the engine by allowing it to heat more 
rapidly and keeping it nearer a constant temperature, 
thus preventing condensation of the fuel, eliminating 
carbon and fouling of spark plugs. 
























































































































65 


WATER COOLING SYSTEM 


the front of the radiator, which regulate the 
amount of air that passes through it. 
These shutters may be controlled by hand 
from the dash, through an operating rod and 
bell crank, or may be connected to the throttle 
control lever. When the engine is running 
slowly the shutters are practically closed. 
When the throttle valve is opened, giving an 
increase in speed and a rise in temperature, 
the shutters will be opened to provide more 
rapid cooling of the water. 

These shutters may also be controlled au¬ 


tomatically by a thermostatic regulator. When 
the water is cold the regulator contracts and 
holds the shutters closed, but as the water 
heats, the regulator expands, opening the 
shutters. This same type regulator may be 
used with a valve to regulate the circulation of 
the water instead of the air. The regulator 
controls certain valves so that when the water 
is cold it circulates only through the engine 
and as the water heats, the regulator expand¬ 
ing opens the valves, allowing the water to cir¬ 
culate through the radiator. 



FIG. 53 

PUMP SHAFT AND DRIVE 




















66 


ENGINES 


WATER PUMPS 

Water pumps used on the internal combus¬ 
tion engine may be either the plunger pump, 
or the gear pump, as explained under lubrica¬ 
tion systems, in which they are more com¬ 
monly used. The centrifugal circulating pump 
is the type most used on the present day auto¬ 
mobile engines. This water pump may be driven 
by a gear and shaft from the generator, or the 
pump shaft may drive the generator. The im¬ 
peller has blades sloping outward to give the 
water a centrifugal or outward whirling action. 
The outlet is on the outer diameter of the 
housing and the inlet near the center. The 
pump circulates the water from the bottom 
of the radiator through the water jackets of the 
engine into the top of the radiator, where it is 
cooled by the air currents passing through the 
radiator as it flows down to the bottom cham¬ 
ber again. The water pump usually has two 
packing nuts to prevent water from leaking 
by the revolving shaft. These packing nuts 
should be packed with candle wick or braided 
cotton, made especially for this purpose and 
well graphited. The bronze bearings are gen¬ 
erally lubricated from grease cups, requiring 
one or two turns once a week. These bearings 
can be replaced when worn. The impeller can 
also be replaced, being mounted on the shaft 
and held in position by a pin or key. Some¬ 
times this pin may become sheared off necessi¬ 
tating replacing with a new pin or kev. (See 
Figs. 2, 5 and 53 for sketch and mounting of 
centrifugal pump.) 

WATER MANIFOLDS 

Both the inlet and outlet water manifolds 
may be made of cast iron, bronze or aluminum. 
The purpose of these manifolds is to provide 
the water connection between the pump and 
the cylinders and between the cylinders and the 
top of the radiator. On a cylinder cast in block 
there will be but one inlet into the cylinder, 
while on the multiple block engine each block 
requires an inlet from this manifold. A mani¬ 
fold may be held on by studs and nuts, or by 
cap screws with a gasket between the two sur¬ 
faces. These surfaces are machined, and the 
asbestos gasket placed in between to prevent 
leakage, or to make up any unevenness in the 
surface. 

RADIATORS 

The principal types of radiators are the 
honey comb or cellular, and the tubular. The 
cellular radiator is constructed of either dia¬ 
mond or square shape cells, with the water 
passing through very small spaces ’surrpund- 
ing them. The tubular type has thin vertical 
tubes for the water to pass down through. This 
space is usually larger than the circulating 


space on the cellular type. The thickness of 
the tubes or the cells determines to a great ex¬ 
tent the efficiency of the cooling system. The 
thinner the metal, the better the heat will radi¬ 
ate. The radiator is constructed with two 
chambers, one the upper and the other the 
lower, connected either by tubes or cells. 

The water leaves the lower chamber and 
passes into the cylinder either by the aid of a 
pump or on the thermo-syphon principle. As 
the water becomes cooler it becomes heavier, 
and this causes it to drop more rapidly. The 
radiator is subjected to considerable vibra¬ 
tion, consequently it is necessary to provide 
some type of shock absorber. The radiator is 
sometimes set on felt packing or plates to ab¬ 
sorb this shock, preventing breaking of the 
soldered joints. In the lowest point of the 
radiator there is usually a drain cock pro¬ 
vided. The purpose of this drain cock 
is to drain the water from the radiator and 
water jackets of the engine. A radiator should 
never be painted because this paint acts as an 
insulation between the cold air and the surface 
of the cooling tube, preventing the cold air 
from coming in direct contact with the surface, 
thereby hindering proper radiation. 

Troubles 

In time, scale will form throughout the in¬ 
terior of the cooling system in both the 
water jackets and the radiator. This scale 
prevents the water from coming in direct con¬ 
tact with the radiating surfaces of the radia¬ 
tor, causing the engine to overheat, resulting in 
a general loss of efficiency. This scale can be 
removed by using either a lye or muriatic acid 
solution. 

When using the lye solution, remove the rub¬ 
ber hose connections, stop up the water outlet 
at the bottom of radiator and the water inlet 
at the bottom of water jackets. Dissolve three 
one pound cans of lye in five gallons of hot 
water and pour into The cooling system, letting 
it stand about five hours. Drain and flush 
the cooling system with a stream from a hose. 
Replace hose connections and refill with clean 
soft water. 

When using the muriatic acid solution, it 
will also be necessary to remove the rubber 
hose connections. Mix 1 part of commercial 
muriatic acid with 7 parts of soft water, pour 
into cooling system and let stand for about 
twenty-four hours. Drain, flush, and refill with 
clean soft water. The engine should not be 
run when these solutions are in the cooling 
system. Always use soft water or rain water 
in the cooling system if possible. 

Tlie scale which forms in the cooling sys¬ 
tem is a lime or mineral deposit. Most all well 




RADIATORS 


67 


water or hard water contains more or less 
mineral matter, this matter being either in 
suspension or solution, and will form a scale 
deposit in the radiator tubes and water jackets. 
Where an anti-freezing solution is used that 
contains some salt as a basis, such as calcium- 
chloride, this circulating through the cooling 
system may deposit solid matter in the form of 
crystals on the inner surface of the cooling 
walls. 

Anti-freezing solutions containing glycerine, 
may have a chemical action, due to the acid 
sometimes found in the cheap commercial 
grades of glycerine used for this purpose. This 
chemical action causes deterioration of the 
water jacket walls and also helps to cause a 
deposit. The glycerine solution will also affect 
the rubber hose. 

Anti-Freezing Solutions 

To lower the freezing point of water to pre¬ 
vent freezing in cold weather, various solu¬ 
tions may be used. Among those more com¬ 
monly used are; common salt, alcohol, glycer¬ 
ine, and calcium chloride. Each of these have 
certain advantages and disadvantages. 

An alkaline solution, such as the salt and 
calcium chloride, produces a distinct electro¬ 
lytic action similar to an electric battery, 
wherever two dissimilar metals are used in the 
cooling system, such as the brass tubing of the 
radiator and the solder at the joints, or the 
aluminum pump housing and the steel impel¬ 
lers. These solutions will also have a tendency 
to leave crystals or an incrustation as the 
water evaporates. The alcohol solution affects 
none of the system, but evaporates very rap¬ 
idly. The glycerine solution affects the rubber 
hose. 

Of the above named substances, perhaps al¬ 
cohol is the preferable one, since it will not af¬ 
fect the metals or rubber and will not form de¬ 
posits of foreign matter, also will not freeze at 
known temperatures and has no electrolytic ef¬ 
fect. But the boiling point of alcohol is very 
low, and this will cause it to evaporate at a 
temperature less than the boiling point of 
water. 

One of the best mixtures, is a solution of 
water, alcohol and glycerine. The addition of 
glycerine will reduce the liability of evapora¬ 
tion to a large extent and raise the boiling 
point. 

Freezing Points 
Water and Alcohol 

Water 95%—Alcohol 5 % ■— Freezing point, 
25° F. 

Water 75%—Alcohol 25% — Freezing point, 
zero. 

Water 60%—Alcohol 40% — Freezing point, 
20° below zero. 


Water, Alcohol and Glycerine 

Water 90%—Alcohol-Glycerine 10%—Freez¬ 
ing point, 25° F. 

Water 75%—Alcohol-Glycerine 25%—Freez¬ 
ing point, 10° F. 

Water 70%—Alcohol-Glycerine 30%—Freez¬ 
ing point, 5° below zero. 

Water 60%—Alcohol-Glycerine 40%—Freez¬ 
ing point, 15° below zero. 

LUBRICATION 

The purpose of a lubricant on any bearing 
surface is to keep metal away from metal. 
With a film of oil between two bearing sur¬ 
faces, the bearing surfaces ride upon the oil 
instead of upon each other, which reduces the 
friction and the wear. Therefore, there must 
always be some clearance between any two 
bearing surfaces to allow for expansion of the 
metals when heated and also for the film 
of oil. Lubricating oil in the internal com¬ 
bustion engine serves three distinct purposes; 
general lubrication of all bearings, compression 
seal and cooling. Without sufficient lubricat¬ 
ing oil on the various bearings the friction will 
increase, causing high temperatures, general 
overheating of the bearings, and as the oil 
becomes hotter and thinner, it lubricates less 
than before. The film of oil between the 
piston and cylinder twall fills the clearance 
space and forms a seal to assist in keeping the 
compressed gases within the combustion 
chamber. Without this seal it would be im¬ 
possible to maintain the compression pressures 
necessary for efficient combustion. 

New bearing surfaces of any type or descrip¬ 
tion when placed under a magnifying glass 
appear to be a mass of high and low spots, 
no matter how well they may be ground or 
finished. The lubricating oil that comes onto 
the bearing surfaces prevents these high spots 
from coming in contact with one another, al¬ 
lowing the high spots to gradually wear off, 
thereby smoothening the surface and reducing 
the friction. If the bearings were run without 
a lubricant or with excessive pressure before 
they are worn smooth, it would cause undue 
friction between the metals, developing heat, 
tearing these high spots off and roughening the 
bearing surfaces. When the bearing surfaces 
become roughened, the bearing can no longer 
be kept tight. 

Under all conditions use the brand of oil 
recommended by the engine manufacturers. 
The manufacturers have made extensive ex¬ 
periments with various brands and bodies of 
oils best suited to their engines, and their 
recommendations should be followed as nearly 
as possible. The oiling system employed pre¬ 
determines the weight or density of oil to be 




G8 


ENGINES 



FIG. 54. 


FORCE FEED LUBRICATING SYSTEM 
SLEEVE VALVE ENGINE 

This system employs a plunger pump mounted on an 
oscillating shaft. A sleeve rod mounted around the 
eccentric shaft through its connection with the plunger, 
moves the plunger back and forth, and up and down. 
As the plunger moves up drawing the oil from the 
sump into the pump shaft, the shaft moves to the right. 
When the plunger reaches its highest point of travel 
the shaft turns clockwise enough to close the inlet at 
the bottom and open the outlet at the top. The plunger 
moves down and forces the oil out of the shaft, by the 
by-pass pressure regulator, to the main bearings of the 
crankshaft, through drilled holes in the crankshaft to 
the rod bearings. The overflow of oil from the connect¬ 


ing rod bearings is thrown by the rapid rotation of the 
shaft up onto the lower ends of the sleeves and pistons. 
Circular grooves in the sleeves gather the oil, and aided 
by the suction, the oil passes from groove to groove 
and through small perforations, lubricating the sur¬ 
face of the sleeves and pistons. The oil pressure is 
automatically regulated by a by-pass valve which is 
controlled from the throttle. That is, as the throttle is 
opened, the cam forces the valve inward which causes 
the spring to hold the by-pass valve tighter against its 
seat. When the throttle valve is in a closed position the 
cam moves around and allows the oil pressure to force 
the valve away from its seat. This prevents an exces¬ 
sive pressure at low speeds. 



FIG. 55. 


FORCE FEED SYSTEM—T-HEAD ENGINE 

A gear pump located outside the engine draws the 
oil from the oil sump and forces it through eL tube to a 
pipe through the crankcase, which conducts the oil to 
the main bearings. The oil is forced into the center of 
the crankshaft and through a drilled hole to the crank 
pin bearing of the connecting rod. 





















































































































































LUBRICATION 


69 


used, thus a splash oiling system has not 
sufficient pressure to force heavy oils through 
the bearing clearances and a lighter oil is 
necessary, while with a pressure system the 
heavier bodied oils can be used. 

In aircraft engines, racing engines, or 
engines where the temperature rises very rap¬ 
idly, oils of fairly heavy body should be used, 
as the flash or burning point is higher. These 
heavier oils do not break down as readily un¬ 
der high temperature as the lighter oils. On a 
heavy duty, constant speed or high speed en¬ 
gine the temperature on the interior of the 
combustion chamber is very high, while on the 
automobile where the engine is working under 
a variable load, the temperature never becomes 
as high. Hence, it is not necessary to employ 
the heavy oils. The heavy oil causes a drag 
in the bearings and increases the carbon de¬ 
posit, if the operating temperature is low. The 
oil used must have a clinging tendency, to re¬ 
sist being forced from between the bearing 
surfaces. 

The most practical and best oils to use in the, 
internal combustion engine are the mineral 
oils, because they withstand the heat and high 
pressures with which they come in contact. 
Vegetable or animal oils have a certain acid 
effect on the metals and also gum up readily, 
producing friction in the engine and prevent¬ 
ing perfect lubrication. 

A certain amount of this oil burns or bakes 
onto the walls of the combustion chamber and 
the head of the piston. This deposits a certain 
amount of carbon residue which makes the 
combustion chamber smaller and results in an 
increase in temperature through having higher 
compression, thereby sometimes causing a 
premature explosion. 

This carbon deposit does not remain red hot 
so there is no tendency to back Are from this 
cause. It will cause the explosions or the ex¬ 
pansion to occur more rapidly so that a partial 
expansion will occur before the piston is on 
T. D. C. If the engine should become over¬ 
heated and enough carbon has been deposited 
in the combustion chamber, it will continue to 
run due to the high compression, even without 
the aid of ati igniting spark. When the piston 
comes up on the compression stroke, if the 
temperature reaches the igniting point, the 
charge is ignited. 

When the engine is first started, being quite 
cold, a large per cent of the fuel taken into the 
combustion chamber may condense or turn 
back into the form of gasoline. This gasoline 
washes the lubricating oil from the cylinder 
walls, allowing the gasoline to pass down into 
the crankcase mixing with the lubricating oil, 
diluting it and making it unfit for use. Lubri¬ 
cating oil diluted with gasoline or kerosene 


does not lubricate the bearings properly, con¬ 
sequently when the lubricating oil becomes 
diluted it will cause the bearings to cut and 
wear. 

Considerable carbon will work down into the 
crankcase with the oil, making the oil very 
dark, which is an indication that it should 
be changed. 

The method of lubrication varies, depending 
upon the speed, load, and heat generated by 
the engine. Production is also taken into con¬ 
sideration and final cost of the engine. Proper 
lubrication of the engine cannot be over em¬ 
phasized. 

The importance of lubrication may be judged 
from the fact that actual service records, cov¬ 
ering a period of almost two years, show that 
90% of all repair bills, outside of wrecks and 
faulty material, were traced either directly or 
indirectly to improper lubrication. 

Proper lubrication is obtained by allowing 
enough clearance at every bearing surface, so 
that as the engine heats up and the various 
moving parts reach their maximum expansion 
under normal running conditions, there will 
be enough clearance to provide for a film of 
oil, which will prevent one bearing surface 
from coming in contact with the other. 

Oil must be supplied on every bearing sur¬ 
face at all times and the oil must be clean and 
of the correct grade as required by that engine. 
Never allow the oil to get below the correct oil 
level in the sump, and see that the pump is 
operating so that the oil is delivered to the 
bearings. This, on the average car, can be de¬ 
termined by observing the pressure or sight 
feed on the dash. 

The correct grade of oil can be determined 
either from the manufacturer’s recommenda¬ 
tion or from a chart of recommendations fur¬ 
nished and obtained directly from reliable oil 
companies. The chart will recommend the 
correct grade of oil to be used both winter 
and summer for practically every make and 
model of car on the market. These recom¬ 
mendations are correct, since they have been 
determined from laboratory and dyamometer 
tests, in which the running temperature of the 
oil at different points in the engine, the temper¬ 
ature and pressure on the different bearings, 
the design of the engine, its purpose and the 
type of lubrication system have been taken 
into consideration. 

Buy the correct grade of oil in sealed cans 
or drums with the name of the manufacturer 
on the container. 

Due to dilution from unvaporized fuel and to 
sediment which may collect in the oil sump, 
tubes, troughs and bearings, it is necessary, 
about once every five hundred to one thousand 



70 


ENGINES 



FORCE FEED AND 
SPLASH SYSTEM 

FIG. 56. 

(At Left) 

In this system a plunger 
pump circulates the oil onto 
the main bearings under pres¬ 
sure. The pump also circulates 
the oil to troughs underneath 
the rod bearings. These troughs 
are extra wide and are made 
a part of the oil pan. Surplus 
oil in the troughs will overflow 
and drain through the outside 
pipes back to the oil sump. 


SPLASH 

CIRCULATING 

SYSTEM 

FIG. 57. 

(At Right) 

In this oiling system 
the oil is circulated 
by a pump to an in¬ 
dicator on the instru¬ 
ment board, then into 
the troughs under¬ 
neath the connecting 
rods. The rods splash 
the oil onto the differ¬ 
ent bearings. This 
sketch shows a con¬ 
struction where two 
troughs supply the oil 
for four rods. 





























































































































































































































































LUBRICATING SYSTEIVIS 


71 


miles to drain the dirty oil from the crankcase. 
Replace with .kerosene and run the engine 
slowly under its own power not more than one- 
half minute. Drain the crankcase again, re¬ 
move the oil pan, scrape and clean the sedi¬ 
ment from the oil pan, spin the engine over by 
hand forcing the kerosene out of the pump, 
tubes and bearings and allow the engine to 
remain open for some time. These precautions 
will prevent any kerosene from remaining in 
the engine which will dilute the new oil. Then 
replace oil pan and refill with new clean oil. 
Do not fill the oil sump above the maximum oil 
level, indicated by a petcock or level gauge. 

On some engines the oil may need to be 
changed more often. Before removing the oil, 
allow the engine to run until the oil reaches 
the lower oil level. Always refill the oil reser¬ 
voir with fresh oil. Mixing fresh oil with the 
old oil will spoil the lubricating qualities of the 
new oil. 

‘Before trying to start the engine, pour a 
small quantity of oil on the head of each pis¬ 


ton, spin the engine over allowing the oil to 
work down to replace the oil that was washed 
away from around the rings. This oil is neces¬ 
sary in order to have compression. Never al¬ 
low the engine to overheat to such an extent 
that the oil will be forced from the bearings 
by unusual expansion. 

LUBRICATING SYSTEMS 

One of the first lubricating systems used was 
the plain splash system, where the oil was 
poured into the crankcase and the connecting 
rods splashed in it. If the oil was at too low 
a level, the connecting rods could not splash 
it and the bearings would burn out. Or if too 
much oil was put in the crankcase, the con¬ 
necting rods would splash too much oil onto 
the cylinder walls, so that an excessive amount 
would be carried into the combustion chamber 
and foul the spark plugs. A mechanical oiler 
was used with this system to keep the oil level 
constant, but as the engine would labor and 
heat up, it would use more oil and the mechan- 



SPLASH CIRCULATING SYSTEM (FORD) 


In this oiling system the oil is 
picked up from the oil sump by the 
revolving flywheel and dropped 
into the funnel at the end of the 
oil pipe. The oil flows through this 


pipe to the timing gears and 
then into the troughs where the 
connecting rods dip. As the troughs 
All, the oil overflows into the oil 
sump. When the connecting rods 


splash the oil out of the troughs it 
is thrown onto the cylinder walls, 
piston pin bearings, crankshaft, 
camshaft bearings and tappets. 































































































































































72 


ENGINES 


ical oiler would not keep the level high enough. 
The result was burned out bearings and scored 
cylinder walls. 

SPLASH CIRCULATING SYSTEM (FORD) 

The oil in this system is circulated by the fly¬ 
wheel, being carried to a funnel shaped tube, 
through which it is distributed to the different 
bearings and gears. The oil flows into troughs 
directly underneath the connecting rods where 
they splash it. The oil Alls the troughs, then 
overflows and runs down into the oil sump. 
The main bearings, camshaft, piston, piston 
pins, and tappets are lubricated by the oil that 
is splashed and whirled around by the connect¬ 
ing rod, and also by the oil vapor in the crank- 



FIG. 59. 

SPLASH CIRCULATING SYSTEM 

In this oiling system the oil is circulated by a pump, 
to an indicator on the instrument board, then into the 
troughs under the connecting rods. The connecting 
rods dip into the oil in the troughs splashing the oil 
onto the main bearings, pistons, piston pins, tappets, 
and camshaft bearings. 

The oil then flows into the oil sump to be circulated 
again by the pump. 


case, but as the pressure increases on these 
bearings, it forces the oil out, causing them to 
wear very rapidly. 

SPLASH CIRCULATING OILING SYSTEM 

In this oiling system there is a mechanically 
operated pump circulating the oil to the 
troughs for the connecting rods. The oil 
splashed by the connecting rods lubricates 





FIG. 60. 


FORCE FEED AND SPLASH SYSTEM 

In this system the pump circulates the oil onto the 
main bearings under pressure. The oil is thrown from 
the oil troughs by the connecting rods onto the pistons, 
piston pins, tappets, and camshaft. From there it flows 
into the troughs below the connecting rods; the con¬ 
necting rod bearings are oiled by dipping into the 
troughs. 


















































































































































LUBRICATING S.Y STEMS 


73 


the piston, piston pin, camshaft, tappets, 
and the main bearings, then it overflows the 
troughs and drops into the oil sump to be cir¬ 
culated again by the pump. The circulating 
pump keeps the oil at a constant level at all 
times in the troughs. The connecting rods 
dip approximately 3/32" into this oil. If they 
dip deeper, it will flood the cylinder walls, caus¬ 
ing the spark plugs to foul, and also causing 
excessive carbon formation. Some type of 
indicator is used to indicate whether or not the 
oil is being circulated. A pressure gauge may 
be used, but on account of the oil pipes being 
open where they lead into the oil troughs, the 
pressure indicated will be very low. There are 
sight feed indicators used where the driver 
can see the oil passing through the glass 


tube. The oil level gauge which is placed in the 
pan indicates the amount of oil that is in the 
oil sump. 

FORCE FEED AND SPLASH OILING 
SYSTEM 

On this oiling system a mechanically opera¬ 
ted pump of either the plunger or the gear type 
may be used to circulate the oil. The con¬ 
necting rods receive the oil by dipping into the 
troughs, while the main bearings on the crank¬ 
shaft are lubricated under pressure. The oil 
pipe leads directly onto the bearings, so with 
the heavy pressure, it can be seen that the oil 
will reach all the bearing surfaces more readily 
than if it came on by gravity. 

The pressure gauge will indicate a higher 



FIG. 61. 


FULL FORCE FEED SYSTEM 


Oil is forced by the pump direct to the crankshaft 
bearings and by means of drilled holes in the crank 
webs, to the crank pins, then through the oil pipe at¬ 
tached to the connecting rods, to the piston pins. 


The pistons and cylinders are luhricated by the oil 
thrown from the lower end of the connecting rods. 
The oil then returns to the sump and is again circulated. 

This is the only oiling system in which the oil is 
forced onto the piston pin under pressure. 


















































































































































































































































74 


ENGINES 


pressure on this than on the previous system. 
To prevent the bearings from receiving ex¬ 
cessive oil there is a by-pass provided in the 
outlet so that when the pressure reaches a pre¬ 
determined point, a safety valve, which is ad¬ 
justable, will open and allow the excessive oil 
to pass back into the oil sump without going 
onto the bearings. This also prevents exces¬ 
sive oil from reaching the cylinder wall. 

FORCE FEED OILING SYSTEM 

On the pressure oiling system, a mechani¬ 
cally operated pump draws the oil from the 
oil sump, circulates it through pipes to the 
main bearings on the crankshaft. The crank¬ 
shaft is drilled, the holes leading to the crank 



FIG. 63. 

FORCE FEED AND SPLASH SYSTEM 



FIG. 62. 

FORCE FEED LUBRICATING SYSTEM 

The oil is drawn from the oil sump into the pump 
and is carried around by the teeth on the gears and 
forced out to a pipe through the crankcase. The oil 
passes through this pipe to the main bearings, then 
through drilled holes in the crankshaft to the rod bear¬ 
ings. Through another pipe the oil is forced into a 
recess located around and above the camshaft. From 
there the oil feeds by gravity to the camshaft bearings 
and timing gears. The piston, piston pin and cylinder 
walls, etc., are lubricated by the oil vapor which is 
thrown around by the rod bearings. 

The extra oil drains back into the oil sump where it 
is again circulated through the engine. The connect¬ 
ing rods do not dip in the oil. 

With this construction the oil screen can be removed 
and cleaned, also the pump can be removed and adjust¬ 
ments or replacements made wuthout removing the oil 
pan. 
















































































LUBRICATING SYSTEMS 


75 


pin bearings, so that when the oil from the oil 
pipe comes onto the main bearings it lubricates 
the main bearings, then as each small hole that 
is drilled in the crankshaft comes in line with 
the oil pipe, the oil, being under high pressure, 
is forced into the hollow crankshaft and 
through it onto the crank pin bearings. 

The regulating by-pass is more essential on 
this system than on the others, to prevent ex¬ 
cessive oil from getting onto the cylinder walls. 
Where the pressure oiling system is used the 
connecting rods and main bearings are usually 
not fitted with shims, as the oil would get by 
the shims and flood the cylinders. Some pres¬ 
sure oiling systems are constructed with a tube 
fastened onto the connecting rod, which leads 
from the crank pin bearing up to the piston pin, 
so that when the hole in the crank pin lines up 
with this tube the oil will be forced up through 
the tube onto the piston pin. The latter sys¬ 
tem is called the full force feed oiling system. 


Some manufacturers have improved on this 
system by lubricating the camshaft bearings 
under pressure; or the oil may first be forced 
through a hollow camshaft, lubricating its 
bearings and then forced onto the main bear¬ 
ings and connecting rods. With the full pres¬ 
sure oiling system, the bearings retain their 
proper fit for a longer period, because at all 
times there is a positive feed .of oil to the 
bearings. The pressure usually carried in the 
full pressure oiling system is about thirty 
pounds, although on racing and aircraft en¬ 
gines the pressure may be as high as one hun¬ 
dred pounds. 

Oil Level Regulation 

On some engines the oil troughs are hinged 
and their position is governed by the different 
engine speeds; so that as the engine speeds 
up the connecting rods will dip deeper into 
the oil, and as the engine slows down they will 



A. 

Camshaft. 

I. 

Ball check valves. 

B. 

Eccentric. 

J. 

Gaskets. 

C. 

Plunger or piston. 

K. 

Pump housing. 

D. 

Plunger spring. 

L. 

Opening for drain cock. 

E. 

Pump housing flange. 

N. 

Outlet pipe. 

F. 

Packing gland nut. 

0. 

Copper tubing. 

G. 

Inlet pipe. 

P. 

Coupling nut. 

H. 

Ball check valve stop pin. 

AA. 

Flared tube coupling. 
























































































76 


ENGINES 



FORCE FEED OILING SYSTEM—DRY SUMP 










































































































































































































































LU B R I C A TING SYSTEMS' 


77 


FORCE FEED OILING SYSTEM—DRY SUMP 

FIG. 65. 

(See Opposite Page) 

In this system the oil is drawn from the tank by the 
upper pump and distributed through the feed pipe to the 
main bearings under pressure and then through the 
hollow crankshaft onto the connecting rod bearings. 
The oil is then thrown onto the cylinder walls and 
piston pins. The extra oil drops down into the oil sump. 
An oil pipe carries some of the oil into the hollow over¬ 
head camshaft and through small holes onto its bear¬ 
ings. The extra oil passes through the camshaft hous¬ 
ing onto the beyel timing gears and down through the 
vertical shaft and housing onto the lower bevel gears, 
then into the oil sump. From there the oil passes 
through the screen and into the lower pump which 
forces it up into the tank again. 


the oil above the low level mark, but never 
above the high level mark. Should the oil be 
above the high level mark, the connecting rods 
would dip too deep into the oil, flooding the 
cylinders and causing the spark plugs to foul 
and misfire. 

OIL PUMPS 

The purpose of the oil pump in the internal 
combustion engine is to circulate the oil to the 
different bearings in the engine where it will 
overflow and drop back into the oil sump to be 
circulated again. The oil pumps that are used 
are of two distinct types, the plunger pump and 
the gear pump. The plunger pump necessi¬ 
tates a reciprocating drive, while the gear 
pump necessitates a revolving drive. 


not dip as deeply. There is an oil level gauge 
provided on the oil pans to indicate the amount 
of oil that is in the crankcase. Always keep 


Plunger Pump 

The plunger pump is the easier to install 
and does not necessitate gears. It is usually 
driven from the camshaft by means of an 




Oil Outlet. 


Filter screen 


chectf ra/res 


To disconnect strap 'remote 
cotter and unscreiv p/n. 


-Plunder 




Pump t>od(^- 


Oil inlet 


FIG. 66. 

PLUNGER OIL PUMP 








































78 


ENGINES 


eccentric. This eccentric is round,'but being 
set off the center of the camshaft imparts a 
reciprocating motion to the plunger. The 
plunger sets into the pump body, fitting snugly, 
and has a stiff spring resting against a shoulder 
on it to keep it against the eccentric. The 
eccentric forces the plunger down while the 
spring forces it up as the eccentric revolves. 
There may be either one or two check valves in 
the pump. One allows the oil to enter the 
pump, the other allows it to flow out. These 
pumps should be placed down in the oil, or at 
least below the oil level, otherwise at times 
they may drain, necessitating priming before 
starting. They may be placed on the side of 
the crankcase as close to the camshaft as pos¬ 
sible. In assemblies of this kind it is advisable 
when the engine starts, to see that pressure is 
registered on the pressure gauge, or that the oil 
is circulating through the sight feed on the 
dash. Oil pipes leading to and away from the 
pump should be air tight, especially on the in¬ 


let. If this pipe leaks the pump will draw air 
instead of oil. The plunger should be a snug 
fit in the housing. 

Gear Pump 

The gear pump has two gears on the in¬ 
terior and is driven by a shaft. The capacity 
of a gear pump depends upon the speed at 
which it is driven, the width of the face of the 
gears, the number of teeth in the gears, and 
the spacing of the teeth, also the closeness 
with which the gears fit the housing. It is the 
space between the teeth that acts as the oil 
conveyors. The oil is carried from the oil 
inlet around the outside of the gears to the op¬ 
posite side and then forced out the outlet. A 
gear pump will circulate a greater quantity 
of oil than the plunger pump, but will not 
draw oil as far. The plunger pump is the 
better suction pump of the two. Keep the 
pump shaft and the gears fitting snugly 
in the housing to prevent leakage. The 


FIG. 67. 



A. Pumpshaft. 

B. Packing nut. 

C. Packing. 

D. Removable bushing. 

E. Body screw. 

F. Pump base. 


GEAR OIL PUMP 

G. Oil inlet. 

H. Pump body. 

I. Coupling. 

J. Idler gear pin. 

K. Gasket. 

L. Idler gear. 

M. Drive gear. 


N. Coupling nut. 

O. Outlet pipe. 

P. Pressure regulating screw. 

Q. By-pass valve spring. 

R. By-pass outlet. 

S. By-pass valve. 

































































OIL PUMPS — FUEL SYSTEM 


79 


heavier the oil the higher the pressure 
will be. If the oil pump should be on the 
exterior of the engine, it will necessitate a 
packing box or packing nut to prevent the 
oil from being forced out around the pump 
shaft. This packing nut should be packed 
with candle wick or braided cotton, made 
especially for this purpose and well saturated 
with graphite. The graphite prevents the 
shaft from wearing excessively and also will 
keep the packing soft. Adjust the packing 
nut just tight enough to prevent leakage. 

FUEL SYSTEM 

There are several types of fuel systems used 
to feed the gasoline from the main gasoline 
supply tank to the carburetor. The simplest 
and best known is the gravity system. In the 
gravity system the gasoline tank is placed 
above the carburetor so that the gasoline level 
in the float chamber can be kept constant by 
the weight of the liquid. There are baffle 
plates provided on the interior of the tank to 
prevent splashing of the gasoline. To allow 
the gasoline to flow down into the carburetor, 
it is necessary that a hole be drilled in the filler 
cap as an air vent so that air may enter the 


tank as the gasoline flows out. If no vent is 
provided the gasoline will not flow. 

Where the main gasoline tank is lower than 
the carburetor either a pressure or vacuum 
system is necessary. The tank being lower, 
the gasoline must be lifted to supply the car¬ 
buretor. In the pressure system the pressure 
must not be above five pounds, as any pres¬ 
sure above may force the float needle valve in 
the carburetor away from its seat and the gas¬ 
oline would overflow the spray nozzle. The 
gasoline would then be picked up by the in- 
rushing air making the mixture too rich and 
cause misfiring. 

There is a safety valve provided either in the 
tank or close to the pressure pump, by which 
the pressure can be regulated. When the 
'pressure reaches the point to which the valve 
has been adjusted the valve will open and 
allow the excessive air to escape. The pump 
used for this pressure system is usually a 
plunger pump and driven by the engine. 

The filler cap of the main gasoline tank in 
the pressure system has no holes drilled in it 
but seats on a gasket to make the tank air 
tight. An auxiliary hand pump and pressure 
gauge are usually provided. If for some rea- 



GRAVITY FUEL SYSTEM 


A. Inlet manifold. 

B. Carburetor. 

C. Float chamber. 

D. Fuel pipe. 

E. Shut off valve. 

F. Screen. 


G. Fuel tank. 

H. Filler cap. 

I. Air vent hole. 

J. Car frame. 

K. Fuel tank supports, 














































































80 


ENGINES 


son the pressure drops too low, the hand pump 
may be employed to restore or maintain the 
necessary pressure. 

Another fuel system is the vacuum system. 
One of the vacuum systems depends upon 
the vacuum that is produced in the inlet 
manifold to draw the gasoline from the main 
supply tank, which may be located below the 
carburetor level. This type of vacuum sys¬ 
tem works very successfully on the automo¬ 
bile engine, but not as successfully on high 
speed engines, or any engine that runs at 
a constant speed on a wide open throttle, be¬ 
cause when the throttle valve of the carbure¬ 
tor is wide open, the vacuum in the inlet mani¬ 
fold decreases and will draw less gasoline at 
the time when the engine needs the most. 

The gasoline tank on the vacuum system 
must have an air vent in the filler cap. There 
must be no air leaks in the pipes. On the 


pressure system air would escape through 
the leaks instead of entering the tank, but on 
the vacuum system air will be drawn through 
the pipes instead of gasoline. 

In the gasoline line there is a strainer to pre¬ 
vent dirt from passing into the tank and into 
the carburetor. This dirt would plug up the pas¬ 
sages, causing the mixture to be too lean, 
and may prevent the engine from running. 
There is usually a sediment chamber provided 
in the gasoline line so that dirt of any kind that 
passes through the pipes will settle in it. This 
chamber and screen should be removed occa¬ 
sionally and the dirt cleaned out. Dirt in the 
gasoline line may cause the engine to misfire 
or back-fire through the carburetor. 

VACUUM TANK 

The vacuum tank commonly used on auto¬ 
mobiles consists of two chambers, the upper 



A. Inlet manifold. 

B. Carburetor. 

C. Fuel pipe. 

D. Air pipe from pressure pump. 

E. Pressure gauge. 

F. Air pipe. 

G. Hand air pump. 

H. Check valve. 

I. Fuel tank. 

J. Filler cap. 

K. Pump crankshaft. 

L. Connecting rod. 

M. Piston. 

N. Cylinder. 

O. Air pipe to the fuel tank. 


FUEL 

SYSTEM 

P. 

Check valve. 

Q. 

Air inlet valve. 

R. 

Relief port. 

s. 

Safety valve. 

T. 

Pressure regulating screw 


For this fuel system to operate properly it is necessary 
for all joints and connections to be air tight. The re¬ 
quired pressure is about five pounds. This pressure is 
maintained by the air pump driven by the engine. The 
hand pump (G) is used to force air into the tank to 
supply enough gasoline to the carburetor to start the 
engine or maintain the necessary pressure. Pressure 
regulator (T) is provided to keep the pressure in the 
tank constant, which is necessary as the carburetors 
will not operate under a higher pressure. 




















































































FUEL SYSTEMS 


81 


and lower, the upper acting as a filling cham¬ 
ber and the lower acting as a gravity supply 
tank. The upper chamber has four open¬ 
ings in the top and contains the fioat and oper¬ 
ating mechanism. From one opening a pipe ex¬ 
tends back to the gasoline tank at the rear of 
the car. This is the gasoline inlet. From 
another opening a pipe leads to the inlet 
manifold which allows the vacuum to extend 
into the upper chamber. In the third open¬ 


ing is a pipe, bent in the form of a half circle, 
which allows air at atmospheric pressure to 
enter the two chambers. Into the fourth open¬ 
ing a filler plug is threaded. 

The lower chanlber is usually provided with 
three openings; one at the top and two at the 
bottom. This chamber supplies the gasoline 
by gravity to the carburetor as it is required. 
The lower chamber must be under atmospheric 
pressure at all times, to allow the fuel to flow 



VACUUM FUEL SYSTEM WITH AN ENLARGED VIEW 
OF VACUUM TANK 


A. 

Main fuel tank. 

1. 

Filler plug. 

Q. 

Upper chamber or vacuum tank. 

B. 

Filler cap. 

J. 

Screen. 

R. 

Lower chamber or gravity tank, 

C. 

Vent hole. 

K. 

Cover. 

S. 

Flapper valve. 

D. 

Valve. 

L. 

Gasket. 

T. 

Fuel pipe to carburetor. 

E. 

Fuel pipe. 

M. 

Air passage. 

U. 

Fuel inlet to carburetor. 

F. 

Vent pipe. 

N. 

Metal float. 

V. 

Float chamber. 

G. 

Atmospheric valve. 

0. 

Toggle springs. 

w. 

Inlet manifold. 

H. 

Vacuum valve. 

P. 

Vacuum pipe. 

X. 

Carburetor air inlet. 































































































































82 


ENGINES 



FIG. 71 

PRESSURE OPERATED 


A. 

Engine cylinder connection. 


B. 

Fuel tank connection. 

C. 

Carburetor connection. 


D. 

Gasket. 

E. 

Shut-off valve housing 

F. 

Shut-off valve shaft. 
Compression cylinder. 


H. 

i 

I. 

Piston. 

1 

J. 

Spring. 


K. 

Gasoline inlet pipe. 


L. 

Tank body. 


M. 

Lock niit. 


N. 

Ball check valve. 


O. 

Outlet check valve housing. 


P. 

Outlet check valve seat. 


Q. 

Outlet check valve. 


R. 

Outlet check valve spring. 


S. 

Check valve cap. 


T. 

Check valve spring. 


U. 

Check valve body. 


V. 

Check valve. 


W. 

Float. 


X. 

Shut-off valve shaft air passage. 

Y. 

Shut-off valve housing air 

passage. 
































































































































































































































FUEL SYSTEMS 


83 


from it by gravity. Atmospheric pressure is 
maintained through the space between the 
two chambers, and an air passage which con¬ 
nects the lower chamber to the air vent that 
enters the upper chamber. From one of the 
openings at the bottom of the lower chamber, 
a pipe leads to the carburetor and in the other 
opening a drain plug or valve may be provided. 

Operation 

(See Fig. 70) 

Consider that the float (N) is at the bottom 
with the atmospheric valve (G) closed and the 
vacuum valve (H) open. The suction from the 
manifold produces a vacuum which draws the 
gasoline from the gasoline tank through the 
fuel pipe (E) into the upper chamber. As the 
gasoline level rises in the upper chamber, the 
float (N) moves up and acting through levers 
and springs opens the atmospheric valve (G) 
and closes the vacuum valve (H). Since the 
suction is now cut off, the gasoline in the upper 
chamber will flow into the lower chamber by 
gravity, due to atmospheric pressure in both 
chambers. When the gasoline level lowers to 
a certain point, the float mechanism will close 
the atmospheric valve again and open the 
vacuum valve. The vacuum produced in the 
upper chamber will now draw the gasoline 
from the gasoline tank into the upper chamber, 
as before. 

Troubles 

In the vacuum tank, if the float is punctured 
or stuck-down and does not move up when the 
gasoline reaches its maximum level, the air 
valve will remain closed and the vacuum valve 
open, and the gasoline from the main fuel tank 
will continue to be drawn into the upper cham¬ 
ber, then into the manifold, flooding the cylin¬ 
ders with gasoline. 

If the connections are not air tight, or if the 
air valve does not seat properly, the suction 
from the manifold will draw air from the 
outside instead of gasoline from the tank, 
causing backfiring in the carburetor and mis¬ 
firing due to a lean mixture. Back-firing in 
the inlet manifold may cause the gasoline to 
be forced out through the air vent at the top 
of the tank. 

The vacuum valve prevents air from entering 
the inlet manifold through the upper cham¬ 
ber during the time the gasoline is flowing from 
the upper to the lower chamber, thus prevent¬ 
ing a lean, mixture or back-firing. 

Sometimes when the car stands idle the gas¬ 
oline will drain from the vacuum tank, due to 
loose connections or obstructions under the 
carburetor float needle valve. When this oc¬ 
curs it is necessary to prime the tank before 
startmg. This is accomplished on some cars 
by a hand pump, while in others it is accom¬ 


plished by removing the primer plug and pour¬ 
ing in sufficient gasoline. 

PRESSURE OPERATED TANK 

The pressure operated tank was designed to 
be used in place of the conventional vacuum 
tank in a vacuum fuel system. The vacuum 
tank, operated by the negative pressure or 
vacuum in the inlet manifold above the throttle 
valve, has a tendency to keep an insufficient 
supply of gasoline in the tank at the higher 
engine speeds. At the high speeds when the 
engine demands the maximum amount of 
gasoline, there is a minimum negative pressure 
or vacuum in the manifold, which results in a 
sluggish action of the vacuum tank. The 
pressure operated tank is actuated by the com¬ 
bustion pressure in the cylinder and will oper¬ 
ate and supply gasoline in direct proportion to 
the engine speed. 

Operation 

(See Fig. 71) 

The check valve body (U) is threaded into 
the cylinder head. The pipe from (B) extends 
back to the main fuel tank at the rear of the 
chassis. The main tank has an air vent so that 
it is at atmospheric pressure. The small tank 
has an air vent also, and being mounted above 
the carburetor allows the gasoline to flow by 
gravity to the float chamber of the carburetor, 
through the connection at (C). 

When the float (W) is down, the air pass¬ 
ages (X) and (Y) are in line, so that the ex¬ 
plosive pressure from the combustion chamber 
acts upon the piston (I), forcing it downward 
and compressing the spring (J). At the com¬ 
pletion of the power and exhaust strokes, when 
the pressure in the combustion chamber low¬ 
ers to that of the atmosphere, the spring (J) 
forces the piston (I) upward, causing a 
vacuum in the cylinder (H) below the piston. 
The ball check valve (N) is then forced from 
its seat by the gasoline in the inlet pipe (K), 
which is under atmospheric pressure in the 
main gasoline tank, and rushes in to fill up the 
cylinder (H) until the pressures are balanced. 

The next explosion in the combustion cham¬ 
ber forces the piston (I) downward again, 
closing the check valve (N) and opening the 
valve (Q), forcing the gasoline out of the cylin¬ 
der (H) into the tank. The float (W) rises 
and falls with the level of gasoline in the tank. 
As it rises it turns the shut-off valve shaft (F), 
throwing the air passages (X) and (Y) out of 
line, shutting off communication between the 
combustion chamber and the cylinder (H). 
When the gasoline level lowers enough, the 
shaft (F) turns until the air passages are in 
line again, when the operations in the tank are 
repeated. 



STEWART VACUUM SYSTEM 


84 


ENGINES 











































































































































CARBURETION 


85 


CARBURETION 

The process of carburetion is the combining 
of the vapors which rapidly evaporate from 
hydro-carbon liquids with certain proportions 
of air to form an inflammable gas. The quanti¬ 
ties of air required vary with different liquids, 
as some mixtures burn quicker than others. 
Mixtures of gasoline and air burn very quickly, 
in fact the combustion is so rapid that it is 
practically instantaneous and if caused to oc¬ 
cur in a closed receptacle results in an “ex¬ 
plosion.” 

The mixture must be properly proportioned 
or the rate of burning will vary; if it is too rich 
or too lean the power of explosion is reduced 
and the force acting on the piston is decreased. 
The chemical composition of the fuel deter¬ 
mines the proportion of air required. The 
ordinary gasoline used contains about 84% 
carbon and 16% hydrogen. Air contains oxy¬ 
gen and nitrogen, and the former combines 
with the hydrogen and carbon of the fuel to 
make possible the process of combustion. 

In determining the amount of air necessary 
for the proper mixture, reference is made to 
the fact that one pound of hydrogen requires 
eight pounds of oxygen to burn it, and one 
pound of carbon requires two and one-third 
pounds of oxygen to burn it. Air contains one 
part of oxygen to three and a half parts of 
nitrogen, so for each pound of oxygen needed 
four and a half pounds of air must be used. 
Then to insure combustion of one pound of 
gasoline, nine pounds of air must be supplied 
to burn the carbon, and six pounds of air to 
burn the hydrogen. This is a proportion of fif¬ 
teen pounds of air to one pound of gasoline. 
At 62 degrees Fahrenheit, about fourteen cubic 
feet of air will weigh one pound, so that a 
pound of gasoline will require about two hun¬ 
dred cubic feet of air. This would be the 
amount required for theoretical combustion, 
but in general practice about twice that 
amount is necessary, since the nitrogen, which 
is the main constituent of the air, acts to deter 
the burning. 

In order to be explosive, gasoline vapor must 
be combined with definite quantities of air. 
Rich mixtures ignite quicker, produce more 
heat and more effective pressure on the piston 
head. Mixtures varying from one part gaso¬ 
line and seven parts air to one part gasoline 
and thirty parts air are the limits of a com¬ 
bustible gas. The correct amount is between 
twelve and sixteen parts of air to one part of 
gasoline. The rich mixture (twelve or less to 
one) results in fuel wasted, leaves a carbon 
deposit and is shown by black smoky exhaust. 
The lean mixture (sixteen or more to one) is 
slow burning, resulting in loss of power, and 
ignites incoming gas as shown by back-firing 


in the carburetor; the rich mixture gives the 
greatest power, while the lean mixture gives 
the greatest economy. 

CARBURETORS 

The purpose of the carburetor is to provide 
means for mixing the air and gasoline in the 
proportions required by the engine. Practically 
all the carburetors used at present are of the 
“spray nozzle” type and make use of the fol¬ 
lowing parts: 

Float chamber 
Float 

Mixing chamber 
Venturi tube 
Float needle valve 
Spray nozzle 

Spray nozzle needle valve 
Main and auxiliary air inlets 
Throttle valve 

The current of air is drawn through the mix¬ 
ing chamber, where it mixes with the gaso¬ 
line. A jet or spray nozzle is located in this 
chamber to spray the fuel as it is drawn into 
the air current and thus better vaporize it. The 
size of the air passage at the point where the 
spray nozzle is located is reduced by making it 
of special form called a “venturi tube.” The 
principle of the venturi tube is that when any 
fluid passes through a tube, the volume passing 
will be the same at all points if the size is con¬ 
stant. If the size changes at some point, the 
volume remains the same, while the velocity 
will be inversely proportional to the area. 
Thus, in the restricted portion of the air pass¬ 
age in the mixing chamber the air velocity is 
increased. 

As previously stated in explaining the four 
stroke cycle engine principles, the charge of 
gas is forced into the cylinder due to the fact 
that the atmospheric pressure outside is higher 
than that of the vacuum in the cylinder caused 
by the downward movement of the piston. The 
'velocity of the entering gases thus depends 
upon this difference in pressures, which varies 
with engine speed, and as it slows down it will 
not pick up as much fuel as when running at a 
higher speed. The venturi tube was introduced 
to insure a sufficient supply of gas at the low 
speed by causing the air to pass the spray 
nozzle at a velocity that would pick up the 
necessary amoupt of fuel. 

The main air inlet supplies the air in suffi¬ 
cient quantities for low speeds, but when the 
engine speed increases, the suction in the mix¬ 
ing chamber increases, picking up so much of 
the fuel that the mixture becomes too rich. 
For high speed then, more air is needed and it 
is supplied through one or more auxiliary air 
inlets, usually placed above the spray nozzle 
and below the throttle valve so that the addi- 




86 


ENGINES 


tional supply of air does not affect the spray 
nozzle. 

The auxiliary air valve is adjustable to allow 
regulation of the amount of air entering the 
mixing chamber, and is usually operated by 
the suction of the engine. In some carbu¬ 
retors the auxiliary air valves are arranged to 
operate the spray nozzle needle valve so that 
the mixture of air and gasoline may be made 
more nearly in the proper proportion for the 
various engine speeds. 

An adjustable needle valve is usually placed 
in the spray nozzle, the purpose of which is to 
regulate the amount of gasoline that can be 
drawn from the spray nozzle by the inrushing 
air. 

The breaking up and vaporizing of the fuel 
depends upon the shape of the spray nozzle 
and the needle valve. If the valve has a fine 
and long point on it, the fuel must pass through 
a longer space, which helps to vaporize it. If 
the point is blunt, the fuel will pass through a 


larger space and will not be broken up as 
thoroughly. The thread on the needle valve is 
of very fine pitch so that a slight change in the 
valve does not give too great a change in the 
mixture. In some cases the valve is adjusted 
definitely by hand and in other cases its adjust¬ 
ment is automatically provided for in the oper¬ 
ation of the auxiliary air valves. When so 
operated it is called a “metering pin.” 

Carburetors may have one or more spray 
nozzles or jets. The jets are small tubes with 
openings of various specified sizes. The jet is 
used to make it impossible for the car driver 
to change the adjustment of the carburetor 
without obtaining special wrenches. Some 
carburetors have a single jet for all speeds, 
while others have low and high speed jets or 
needle valves. 

The purpose of the float chamber is to hold 
a small quantity of gasoline in close prox¬ 
imity to the spray nozzle and where it can be 
maintained at a constant level. It takes its 



A. 

Gasoline inlet. 

K. 

B. 

Float chamber. 

L. 

C. 

Float chamber cover. 

M. 

D. 

Float. 

N. 

E. 

Float needle valve. 

0. 

F. 

Float needle valve seat. 

P. 

G. 

Priming lever. 

Q. 

H. 

Float valve lever arms. 

R. 

I. 

Gasoline passage. 

S. 

J. 

Gasoline jet. 

T. 


CARBURETOR—SINGLE JET 


Gasoline level. U. 

Gasoline adjusting valve. V. 

Packing nut. W. 

Venturi tube. X. 

Mixing chamber. Y. 

Throttle valve lever arm. Z. 

Throttle or butterfly valve. 

Stop screw. 1. 

Choke valve. 2. 

Main air inlet. ' 


Auxiliary air valve. 

Auxiliary air valve spring adjustment. 
Lock nut. 

Auxiliary air valve spring. 

Auxiliary air valve seat. 

Carburetor flange. 

Float needle valve guide. 

Spray nozzle. 







































































































CARBURETORS 


87 



FIG. 74 

CARBURETOR, COMPENSATING TYPE 
ZENITH 


A. 

Throttle valve. 

J. 

Float. 

B. 

Throttle shaft. 

L. 

Compensator. 

C. 

Venturi or choke tube. 

O. 

Screen. 

E. 

Idling device. 

P. 

Coupling. 

F. 

Air passage. 

Q. 

Tube .coupling. 

G. 

Main jet. 

R. 

Choke valve. 

H. 

Float needle valve. 

S. 

Flange. 

I. 

Float needle valve seat. 




The adjustments on the Zenith carburetor are the 
venturi or choke tube, main jet, compensating jet and 
the idling adjustment. The size numbers of these parts 
constitute the settings. The size numbers are stamped 
on each part. 

The chokes are numbered in millimeters and the jets 
in hundredths of millimeters. 

Troubles 

Choke tube too large— The pick up will be defective 
and cannot be bettered by the use of a larger compen¬ 
sator. Slow speed running will not be very smooth. 


The engine will have a tendency to load »up under a 
hard pull and at high speed the exhaust will be of 
variable nature. 

Choke tube too small —The effect of a small choke 
tube is to prevent the engine from taking a full charge 
with the throttle valve fully opened. The pick up will 
be very good but it will not be possible to get the 
maximum speed. 

Main Jet too large —At high speed it will give the 
indication of a rich mixture, irregular firing in the 
muffler, sooting up the spark plugs. 

Main jet too small —The mixture will be too lean at 
high speed. There may be backfiring at high speed. 

Compensator too large— Too rich a mixture on a hard 
pull. 

Compensator too small —Too lean a mixture liable to 
misfire and give jerky action to the car on a hard pull. 

Idling adjustment made with the idling screw. If this 
screw must be run in all the way, put in a larger idling 
device. If this screw must be run out all the way put 
in a smaller idling device. 





































































































































88 


ENGINES . 


name from the fact that a float is used to 
operate the valve controlling the flow of gaso¬ 
line into the chamber. The float rises and falls 
as the gasoline level varies and is adjusted so 
that the gasoline will always be kept approxi¬ 
mately at the height of the spray nozzle where 
the air current picks it up. When no air is 
passing through the mixing chamber, the 
gasoline level should be 1/32" to 1/16" below 
the top of the spray nozzle. If too high the 
nozzle will continually overflow and if too low 
the air current will not pick up sufficient fuel. 

The float is made hollow, of very light sheet 
brass or copper, soldered to make it air tight, 
or made of cork. If the hollow float leaks it 
will All with gasoline and becoming too heavy 
to float will settle down, holding the needle 
valve open until the float chamber becomes 
“flooded” and the gasoline overflows at the 
spray nozzle. The cork float is painted with 
three or four coats of shellac to keep the gaso¬ 
line from getting into it. If this coating wears 
off, the gasoline will soak into the cork until it 
becomes “gasoline logged,” preventing it from 
floating and resulting in the flooding of the 
float chamber as mentioned before. 

Different methods are used to connect the 
float with the needle valve controlling the flow 
of gasoline into the float chamber. In Fig 73, 
which illustrates a typical single jet carbu¬ 
retor, there are two float levers pivoted on the 
float chamber cover, one end of each resting 
on the float and the other end connected to the 
float needle valve. As the float rises and falls 
these levers move with it, thus closing and 
opening the valve. In Fig. 75 the float and 
needle valve are secured to a single arm piv¬ 
oted in the center, the result being the same. 

As the gasoline enters the float chamber it 
passes through one or two fine mesh screens. 
These screens strain the fuel, preventing par¬ 
ticles of dirt or other foreign matter from en¬ 
tering the float chamber. Any dirt or lint that 
might settle on the float valve seat would pre¬ 
vent the valve from closing and cause the fuel 
to overflow at the spray nozzle. 

Main Air Inlet Heaters 

The main air inlet of the carburetor is some¬ 
times provided with a hot air tube, which con¬ 
veys the hot air from around the exhaust pipe 
to the air inlet. From there it passes by the 
spray nozzle, vaporizing the fuel more thor¬ 
oughly. The carburetor may have a jacket 
cast around the outside of the mixing chamber 
through which hot water from the engine 
is circulated, helping to vaporize the fuel. 
On some carburetors hot oil may circulate 
through this jacket. 


Throttle Valve 

The purpose of the throttle valve is to regu¬ 
late the amount of the mixture entering the 
combustion chamber, thus controlling the 
speed of the engine. It serves the same pur¬ 
pose as a water valve in a water pipe, or of a 
steam valve in a steam pipe. The valve is 
operated from the driver’s compartment 
through a series of levers and connecting 
links. 

On the throttle valve lever there is a small 
screw provided which is called the stop screw. 
The purpose of this screw is to set the throttle 
valve so that it will not close entirely, in order 
to keep the engine running at a slow speed. 
Sometimes this stop screw is located on the 
outside of the mixing chamber where the 
throttle control lever strikes the screw just be¬ 
fore the throttle valve closes. This prevents 
the engine from stopping when the throttle 
control lever on the steering wheel is in the 
closed position. This stop screw is not a carbu¬ 
retor adjustment. Carburetor adjustments are 
those which regulate the mixture. 

Idling Adjustment 

Due to the low suction at low engine speeds, 
the velocity of the air at the spray nozzle is not 
great enough to draw the heavy fuel and the 
fuel that it does draw has not sufficient 
velocity for proper vaporization. Conse¬ 
quently, at low engine speeds the engine may 
misfire due to an insufficient amount of fuel be¬ 
ing supplied or not properly vaporized. To 
overcome this, some carburetors are provided 
with an idling device which allows the fuel to 
be taken through a by-pass into the mixing 
chamber at the throttle valve. When the en¬ 
gine is running at slow speed, the vacuum 
above the throttle valve is very high, while 
below the throttle valve there is practically no 
vacuum or suction at all. The fuel taken out 
of this idling well or by-pass through the small 
opening under the high vacuum will be vap¬ 
orized, allowing the engine to fire properly at 
slow speed. When the throttle valve is opened 
and the engine speeds up, the suction is not as 
effective upon the small well, as when the 
throttle was closed. 

Gaskets 

Gaskets are made of a compressible material 
and are placed between two surfaces to over¬ 
come unevenness in machining and to prevent 
leakage. A gasket should be used between 
carburetor and inlet manifold to prevent air 
from entering in any other manner than 
through the proper air inlets. Air leaks at any 
point above the throttle make it impossible to 
control the quality of the mixture, making the 
engine hard to start and hard to control. 

Continued on page 95 





CARBURETORS 


89 



FIG. 75 

CARBURETOR, AIR VALVE TYPE 
MARVEL 


A. 

Throttle valve. 

. 1 . 

Float. 

B. 

Throttle valve shaft. 

K. 

Primer. 

C. 

Heater damper. 

L. 

Gasoline adjustment (needle valve). 

D. 

Air valve spring. 

M. 

Throttle lever and heater damper connections. 

E. 

High speed air adjustment. 

N. 

Heater jacket. 

V. 

Exhaust gas inlet to heater jacket. 

O. 

Auxiliary air valve. 

G. 

High speed nozzle. 

Q. 

Gasoline inlet. 

H. 

Float needle valve. 

R. 

Choke valve. 

I. 

Float needle valve seat. 

S. 

Screen. 


ADJUSTMENT OF MARVEL CARBURETOR 


Turn the air adjusting screw inward until the end of 
the screw is flush with the ratchet. Unscrew the needle 
valve one turn. Start the engine, then allow it to warm 
up. Place the spark lever in full retard, adjust needle 
valve until the engine runs smoothly, then place the 
spark lever in advance and open the throttle quickly. 
If the engine skips or stops while accelerating, unscrew 
the needle valve slightly by turning it to the left until 
the throttle valve can be opened rapidly without caus¬ 
ing the engine to skip or stop. 

The air valve adjusting screw need not be further 
adjusted unless the proper acceleration cannot be ob¬ 


tained, More accurate low speed adjustment can be 
made by the needle valve with the engine running 
at low speed and under load. Turn the gasoline 
adjusting valve (L) clockwise until a backfiring in the 
carburetor is noted or a misfiring occurs. Then turn 
the adjustment the other way just enough to prevent 
misfiring or backfiring. Then speed the engine and 
when running at normal driving speed under load, turn 
the air valve oV high speed adjustment (E) to the 
left until a backfiring is noted; turn it the other way 
just enough to prevent a backfiring. This is the max¬ 
imum economy adjustment. 



















































































































90 


ENGINES 



FIG. 7G 


CARBURETOR, PLAIN TUBE TYPE 
STROMBERG 


A. Throttle valve. 

B. Throttle valve shaft. 

C. Large venturi. 

D. Small venturi. 

E. High speed adjusting needle v; 

F. Air bleeder. 


G. Needle valve seat. 

H. Float needle valve. 

I. Float needle valve seat. 

J. Float. 

K. Accelerating well. 

L. Idling tube. 

M. Idling adjustment needle. 


N. Idling discharge jet. 

O. Strainer. 

P. Strainer body. 

Q. Gasoline connection. 

R. Choke valve. 

S. Carburetor flange. 


The adjustments on this carburetor are the high 
speed adjusting screw (E) and the idling adjustment 
needle (M). 

Surrounding and communicating with the tube (L) 
which conducts the gasoline from the measuring orifice 
to the jet, is a circular reserve chamber or accelerating 
well (K). With the engine idling or slowing down, this 
well fills with gasoline and when the venturi suc¬ 
tion is increased by opening the throttle valve or at a 
faster engine speed, the level in the well goes down and 


the gasoline thus displaced passes through the holes in 
(K) to join the flow from (G), thus more than doubling 
the normal rate of feed. The amount and rate of dis¬ 
charge can be graduated by changing the holes in the 
top and side of the well. 

When the throttle is closed, gasoline is drawn in 
through the hole in (L) and mixed with air taken in 
through the hole in the venturi at (M) and discharged 
into the carburetor at the throttle valve. 

















































































































































CARBURETORS 


91 




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92 


ENGINES 


6 



NCCPLC Vj^LVC 

NOZZLC 

TH^OTTLC 

7- 4UZfUAJZr A/Z ^NLCr 
OZAfA/ PLl/a 


FIG. 79 

CARBURETOR, AIR VALVE METERING PIN TYPE 
RAYFIELD 


RAYFIELD CARBURETOR 

The model of Rayfield carburetor shown in Fig. 79 
supplies the fuel through two different passages. One 
supplies all the gasoline required when the engine is 
idling and at low speed. This is through the spray 
nozzle (5). The additional gasoline required for higher 
speeds is furnished through a tube which is controlled 
by a tapered metering pin located under the autornatic 
air valve (7). 

This model has three air inlets, the constant or 
fixed air opening (4) and tw'o automatically controlled 
air valves, which are interconnected. These two valves 
operate together to increase the supply of air propor¬ 
tional to the additional gas supply caused by the in¬ 
creased suction of the engine upon acceleration. 

A piston attached to the upper automatic air valve 
(7) operates in a dash-pot or cylinder of gasoline. When 
the carburetor is in operation the resistance offered to 
any movement of the piston by the gasoline in the dash- 
pot prevents a sudden opening of the air valve, thus 
causing a strong suction on both fuel nozzles as the 
throttle is opened. When the throttle valve is opened, 
the vacuum in the mixing chamber tends to draw the 
air valve away from its seat, opening the other air valve 
located at the bottom below the throttle, and at the 
same time moving the metering pin away from its seat 
and also forcing the piston down. The downward move¬ 
ment of the piston produces a pump action which forces 
gasoline up through the metering pin tube into the mix¬ 
ing chamber, giving ah additional amount of gasoline to 
mix with the additional air entering through the two 
auxiliary air inlets. 


There are two adjustments on this carburetor, low 
and high speed, both being fuel adjustments. These 
adjustments regulate the lift of the metering pin at the 
spray nozzle. The low speed adjustment is the lower 
knurled screw. Turning this screw to the right lifts the 
metering pin from the spray nozzle. The high speed 
adjustment is the knurled screw on the adjustable cam 
which is fastened on the throttle shaft. The cam turns 
with the throttle shaft and does not lift the metering 
pin until the throttle valve is partially opened. Turning 
the screw to the right lifts the metering pin away from 
the spray nozzle. 

With the throttle valve closed, the metering pin lift¬ 
ing arm rests on the flat side of the cam, thereby com¬ 
ing back to the low speed adjustment when the throttle 
valve is closed. 

A dash control for easy starting is mounted on the 
steering column. This control turns the cam which rests 
against the arm that lifts the metering pin away from 
the spray nozzle, thereby allowing a rich mixture to be 
drawn into the cylinder. 

When this control is pulled all the way back, a plun¬ 
ger valve opens a by-pass having two openings, one 
into the throat of the carburetor, the other in the float 
chamber below the fuel level. 

When the engine is cranked and the throttle valve 
closed, the partial vacuum above the throttle valve will 
draw a rich charge of gas from the float chamber. 

This carburetor is water jacketed, the hot water 
passing around the mixing chamber assisting in the 
proper vaporization of the mixture. 





















































































93 


CARBURETORS 



CARBURETOR, AIR VALVE METERING PIN TYPE 
SCHEBLER 


A. Gasoline needle valve. 

B. Needle valve operating lever shaft. 

C. Needle valve operating lever. 

D. Venturi tube. 

E. Spray nozzle. 

F. Float. 

G. Gasoline passages. 

H. Air passages. 

I. Float chamber. 

J. Main air inlet. 

K. Choke valve lever. 

L. Exhaust gas outlet. 

M. High speed air adjustment. 

N. Auxiliary air valve spring. 

O. Auxiliary air valve chamber. 

P. Auxiliary air valve. 

Q. Low speed gasoline adjustment. 

R. Plunger. 

S. Dash pot. 

T. Dash control lever. 

U. Throttle valve. 

Operation 

The gasoline enters the carburetor through the float 
valve into the float chamber (I), through the passages 
(G) to the spray nozzle (E). 

The vacuum produced by the downward movement 
of the pistons draws the gasoline from the spray nozzle 
(E), past the needle valve (A), through the venturi 
tube (D) and the mixing chamber. At the same time 


the suction of the pistons draws the 
air through the air intake (J) and 
passages (H) into the venturi tube. 
Thus the gasoline and air entering at 
high velocity vaporizes more readily 
while the mixture is passing through 
the venturi tube. At higher engine 
speed the increased vacuum in the 
mixing chamber draws the air valve 
(P) away from its seat, allowing more 
air to enter the mixing chamber; and 
as the needle valve (A) is raised and 
lowered automatically by the move¬ 
ment of the auxiliary air valve, more 
or less gasoline is allowed to spray in¬ 
to the mixing chamber. As the air 
valve moves down it lifts the needle 
valve (A), acting through the lever 
(C), admitting more gasoline. The 
needle valve acts as a metering pin, 
admitting an increased amount of gas¬ 
oline in direct proportion to the in¬ 
creased amount of air entering 
through the auxiliary air valve. 

To prevent an erratic action of the 
air valve when the throttle is suddenlv 
opened or closed, a dash pot is used. 
Its function is to steady the move¬ 
ment of the air valve and pre¬ 
vent sudden extreme opening or clos¬ 
ing and also prevent the air valve from 
“chattering” due to the intermittent 
suction developed by the pistons. The 
air valve (P) is connected directly to 
a plunger (R) which operates against 
a cushion of air in the dash pot (S). 

Adjustments 

With the engine under load at low 
speed, turn the adjustment (Q) to the 
left or counter clockwise until the 
engine backfires or misfires, then turn it to the right 
until the engine runs evenly. 

Advance the spark lever two-thirds to three-fourths 
of the travel on the sector and open the throttle quickly. 
If the engine backfires upon this sudden acceleration, 
turn the adjusting screw (M) to the right until the 
engine does not backfire upon acceleration, and runs 
properly at high speeds. When the screw (M) is turned 
inward the spring (N) is compressed, which increases 
its tension, holding the air valve (P) tighter against 
its seat, restricting the amount of air entering by 
the air valve at high speeds and upon acceleration. 
When the adjustment (Q) is turned to the left it lowers 
the needle valve in the nozzle at (E) and decreases the 
amount of gasoline allowed to enter the mixing cham¬ 
ber. 

There is usually a choke lever located either on 
the dash or steering column. This lever is connected 
directly with the needle valve by means of an eccentric 
on (B) in the mixing chamber. When the dash con¬ 
trol lever is moved, it acts through a connecting wire 
and lever (T), which lifts the needle valve (A). When 
the choke lever is moved all the way back a shoulder 
on the lever (T) tries to move the lever (C) upward. 
This causes the air valve (P) to be held against its 
seat. The result is a rich mixture for starting. As 
the engine warms up, move the dash choke lever in 
the opposite direction, gradually lowering the needle 
valve (A). When the engine is warm, the dash choke 
lever should be closed, which will not interfere with 
the regular carburetor adjustments. This carburetor is 
jacketed to allow the hot exhaust gases to assist in the 
vaporization of the fuel. 





























































































94 


ENGINES 



FIG. 81 

CARBURETOR, TWO STAGE MULTIPLE JET TYPE 
BALL AND BALL (TRADE NAME) 


1. Float arm. 

2. Float. 

3. Float needle valve. 

4. Main air inlet. 

5. Jets. 

6. Throttle valve. 

7. Auxiliary air valve. 

8. Swivel fuel pipe connector. 

9. Idling tube. 

10. Idling adjusting screw. 

11. Lower air valve. 

The gasoline level is just below the top of the jets 
(5). As the throttle valve is opened, the air entering 
through the main air inlet (4) draws the gasoline from 
the jets. 

There is no low speed adjustment except by changing 
the size of the venturi and jets. 

Connected with the float chamber at the bottom and 
the mixing chamber at the top is an idling tube (9). When 
the throttle valve is closed, or practically closed, the 
high vacuum above the throttle valve draws the gaso¬ 


line up through the idling tube and into the mixing 
chamber above the throttle valve. There is a small air 
opening at the idling adjusting screw, which allows air 
to enter with the gasoline. This opening is adjustable. 
On some models of Ball and Ball there is an accelerat¬ 
ing well, which is connected to the float chamber at the 
bottom and the mixing chamber at the top. When the 
throttle valve is almost closed there is created a vacuum 
in the top of this tube which draws a plunger upward. 
The upward movement of the plunger draws gasoline 
into the lower part of the tube. When the throttle valve 
is opened suddenly, the vacuum above the throttle valve 
is lost. The weight of the piston as it moves down in 
the accelerating tube forces the gasoline out through a 
jet into the mixing chamber. 

The auxiliary air valve (7), which is adjustable only 
to a limited extent, regulates the mixture at high speeds. 

When the throttle valve is opened wide, the lower air 
valve (11) is opened in the secondary air inlet by a 
connecting lever. Air entering the mixing chamber 
through the secondary inlet, causes additional gasoline 
to be drawn from jets located in this inlet. 

































































































CARBURETORS 


95 


CARBURETOR CONDITIONS 

Engine Starting and Operation 

For easy starting, a choke valve is usually 
provided in the main air passage. By choking 
the main inlet of the carburetor the mixing 
chamber is under a higher vacuum which pro¬ 
duces a very rich mixture. Fuels vaporize at a 
lower temperature in a vacuum than under 
atmospheric pressure. As this vacuum draws 
more fuel from the spray nozzle, it makes the 
engine easier to start. 

When choking the main air inlet on a car¬ 
buretor that is provided with an auxiliary air 
valve, the high vacuum may draw the auxiliary 
valve away from its seat, causing the mixture 
to be too lean, and prevent the starting of 
the engine. One method of overcoming this 
is the use of a mechanical device which draws 
the needle valve away from its seat allowing 

rich mixture to be taken into the cylinder. 
This eliminates the necessity of a choke. 

A mixture that is too lean may cause a back¬ 
fire through the carburetor, except when start¬ 
ing. A back-fire through the carburetor while 
cranking the engine is not caused by the mix¬ 
ture being too lean, but may be caused by the 
ignition not being wired according to the fir¬ 
ing order, the camshaft not .timed correctly, 
or the inlet valve not closing. At low engine 
speeds, or when attempting to start the engine, 
if the mixture is not rich enough it will not fire 
at all. Or, if the engine is running slowly and 
the carburetor is adjusted so that the mixture 
is too lean, the engine will stop without back¬ 
firing. 

The back-fire becomes more distinct as 
^he throttle valve is opened and the compres¬ 
sion and explosive forces become more power¬ 
ful. With a lean mixture and a wide open 
throttle, a back-fire will throw a fiame a con¬ 
siderable distance out of the main air inlet 
of the carburetor, possibly setting fire to the 
stray gasoline that may have been dripping 
from it. 

A rich mixture is indicated by the variable 
engine speed, or what is known as galloping or 
loping, and also by the black smoke which 
issues from the exhaust. (Blue smoke from 
the exhaust is an indication that lubricating oil 
is being burned in the combustion chamber.) 

The engine running at various speeds and 
loads demands various mixtures. More power 
is required to get a load under motion, and 
a richer mixture is needed, while as the engine 
speeds up and gets the load under motion, a 
rich mixture is no longer required. However, 
more gasoline will be consumed as the indi¬ 
vidual cylinders are firing more times per 
minute. 


On carburetors having multiple adjustments, 
always make the low speed adjustment first. 
After the low speed adjustments are made, the 
speed of the engine should be increased and 
the high speed adjustment made. Never make 
final adjustments until the engine becomes 
heated. When the engine becomes heated the 
vaporization of the fuel that is taken in de¬ 
pends largely upon the heat in the combustion 
chamber. 

When the engine is cold it is noticeable that 
the mixture is too lean, hence the engine 
should be run with the choke valve partially 
closed and gradually opened as it becomes 
heated. A mixture that is too lean will cause 
misfiring at low speed, before it causes a back¬ 
fire, while a mixture that is rich may cause 
misfiring. When adjusting a carburetor al¬ 
ways adjust it to the running condition of the 
engine, that is, considering temperature, speed 
and load. 

Continuous dripping of gasoline from the 
carburetor may be caused by a loose connec¬ 
tion where the gasoline pipe connects to the 
float chamber or by the float needle valve not 
seating properly in the bottom of the float 
chamber so that it will not shut off the gasoline 
properly. To remedy this, the float valve should 
be reground to its seat with fine valve grind¬ 
ing compound. The arms in the float chamber 
may be bent, allowing the float to rise too 
high before it shuts off the gasoline. This 
will cause the gasoline to overflow at the spray 
nozzle. 

IGNITION 

The ignition used on the internal combus¬ 
tion engine may be either magneto or battery 
ignition. The magneto ignition is divided into 
several different types such as low tension, low 
tension dual, high tension, high tension dual, 
and high tension duplex. The types of battery 
ignition are either the vibrating spark or the 
single spark ignition. The driving speed of 
these ignition devices varies in the different 
ignition systems. The ignition timer may be 
driven in connection with the generator or the 
pump shaft. The distributor must be wired 
according to the firing order of the engine. 
The secondary wires must lead to the proper 
cylinders, otherwise it will cause back-firing 
through an open inlet valve into the carburetor, 
and thus prevent starting of the engine. 

The ignition can be timed so as to make 
the spark occur earlier or later. On the 
ignition device there is usually an advance 
and retard mechanism provided, which al¬ 
lows the spark to occur on top dead center 
or a little past when cranking the engine, 
and earlier as the engine speed increases. 
This is necessary because of the lapse of time 




96 


ENGINES 


between the occurrence of the spark and the 
fullest expansion of the gases. The higher the 
speed of the engine, the greater distance the 
piston will have moved by the time the burning 
gas has reached its maximum expansion; 
therefore, to obtain the maximum power from 
the fuel, it is necessary to have the fullest ex¬ 
pansion occur immediately after the piston 
passes top dead center. This is accomplished 
by introducing the spark into the cylinder 
earlier. 

Ignition devices for racing and high speed 
engines have a spark advance of about 45°, 
while the average automobile ignition has an 
advance ranging as high as 20° to 30°. 
Whether it is necessary to use the full range 
of advance or not can only be determined by 
putting the engine through a test. If the spark 
is advanced too far when cranking, it will 
cause a kick-back due to a partial expansion 
occurring before the piston reaches top dead 
center. When the engine is running and the 
spark is advanced, the momentum of the fly¬ 
wheel overcomes the force of the explosion 
until the piston passes top dead center. This 
premature explosion causes a very decided 
knock and wearing of the bearings. 

It is noticeable that as the engine heats up 
the spark may have to be slightly retarded. 
This is due to the fact that after the engine 
becomes heated, the gases will burn faster than 
when cold, requiring the spark to be retarded. 
Also when the car is running up hill or pulling 
a heavy load the engine has a tendency to 
knock. This is due to the throttle valve being 
open wider and the engine drawing in a larger 
volume of the fuel mixture, which gives a 
higher compression and greater heating of the 
fuel. This causes the fuel to ignite and expand 
before the piston has reached top dead center, 
the same as when the spark occurs too early. 
This results in a loss of power and is remedied 
by retarding the spark. However, the engine 
should never be run any length of time with 
the spark fully retarded. 

The formation of carbon in the combustion 
chamber causes a knock, due to high compres¬ 
sion and temperature. This premature ex¬ 
plosion cannot be prevented by retarding the 
spark. In cases of this nature the carbon 
should be removed. 

When starting, the spark should occur in 
full retard on top dead center at the end of 
the compression stroke, or a trifle after. This 
will prevent a kick-back or other damage. 

ENGINE STARTING DEVICES 

One of the common methods of start¬ 
ing the engine is with a hand crank. This 
hand crank has notches machined on the end 


to engage with notches machined in either the 
crankshaft or on the crankshaft nut. The 
construction of these notches is such, that as 
the crank is turned in its direction of rotation 
it will readily turn the engine but as the en¬ 
gine starts, it will have a chance to overrun 
the starting crank throwing it out of engage¬ 
ment. However, should the engine kick back, 
as a result of the spark being advanced too 
far, it will drive the starting crank in the 
opposite direction, often breaking the arm of 
the operator and doing other damage. 

Modern automobile engines are provided 
with an electric starting motor. The starting 
motor is mechanically connected to the crank¬ 
shaft or flywheel by means of a sliding gear 
drive, or through a chain and sprockets, or may 
be automatically connected by means of a 
Bendix drive. 

The source of current used to turn the start¬ 
ing motor is a storage battery provided for this 
purpose. The storage battery is kept in a 
charged condition by means of an electric gen¬ 
erator driven by the engine. In some instances 
the same device is used for charging the bat¬ 
tery that is used for cranking the engine, being 
termed a motor-generator. If the engine 
should not start within a reasonable length of 
time, it is not advisable to use the electric 
motor for too long a period. The battery will 
discharge rapidly, because the current flows 
from the battery through the electric motor 
at a high rate. 

TWO STROKE CYCLE ENGINES 

On a two stroke cycle engine, it requires two 
strokes of the piston to complete a cycle of 
operations, one downward and one upward 
movement. * 

Every time a piston reaches top dead center 
an explosion occurs. The explosions are not 
as powerful in this engine as they are in the 
four stroke cycle engine of equal displacement 
due to various reasons. One is that the piston 
does not have sufficient time to take in a full 
charge of fuel; another is that the fuel taken 
into the cylinder is not vaporized as thorough¬ 
ly; and third, as the exhaust stroke is only 
about 100° long, there is not sufficient oppor¬ 
tunity to scavenge the cylinder of all burned 
gases. The burned gases remaining in the cyl¬ 
inder have a tendency to lower the efficiency of 
the fresh gases. The exhaust port being lo¬ 
cated at the bottom of the stroke of the piston 
instead of at the top prevents the upward mov¬ 
ing piston from forcing the burned gases out, 
which results in a general loss in efficiency. 
The two stroke cycle engines are divided into 
two port and three port types. 

The crankcase assists in the performance 







TWO STROKE CYCLE ENGINES 


97 


of the cycle of operations, as the gases are 
drawn into the crankcase before being ad¬ 
mitted into the combustion chamber. This 
causes considerable condensation in the crank¬ 
case. Crankcase compression is one of the 
greatest drawbacks to the two stroke cycle en¬ 
gines. The condensed portion of gasoline re¬ 
maining in the crankcase decreases the volume 
of the mixture entering the cylinder. 

Construction and Operation 

Instead of employing valves as are used in 
the four stroke cycle engine, the two stroke 
cycle engine uses ports placed in the sides of 
the cylinder. These ports are slots in the 
cylinder wall, which are covered and uncovered 
by the movement of the piston. The exhaust 
port connects to the exhaust pipe and the inlet 
port connects to the by-pass leading to the 
crankcase. 

Consider a charge as being in the combus¬ 
tion chamber of the cylinder ready to fire and 
a mixture in the crankcase at atmospheric 
pressure. This mixture was taken into the 
crankcase during the upward movement of 
the piston. The piston starts down, driven by 


the force of the expanding gases (explosion), 
and as it is driven downward, the piston com¬ 
presses the mixture in the crankcase. When 
the piston reaches a point of about 50° before 
B. D. C. the exhaust port is uncovered which 
allows the burned gases to pass out of the cyl¬ 
inder. After 10° or 15° more crankshaft 
travel or about 40° before B. D. C., the 
inlet by-pass port is uncovered. The com¬ 
pressed mixture in the crankcase will then 
enter the cylinder through the inlet by-pass. 
During the upward movement the piston again 
covers the inlet and exhaust ports, the mixture 
in the cylinder is compressed and the vacuum 
formed in the crankcase draws a new charge. 
When the piston reaches T. D. C. it will again 
be at the firing point, having completed the 
cycle of operation. This gives an exhaust 
stroke of approximately 100° and an inlet 
stroke of approximately 80°. 

The exhaust port is uncovered before the in¬ 
let port to rid the cylinder of the burned gases, 
the excessive pressure and heat. On the piston 
head is a deflector, which is placed on the inlet 
side to deflect the incoming fuel charge up¬ 
ward, preventing it from passing out- with 


FIG. 82 


TWO STROKE CYCLE 
TWO PORT ENGINE 


A. Spark plug. 

B. Water jacket. 

C. Combustion chamber. 

D. Cylinder. 

E. Deflector plate. 

F. Inlet port. 

G. By-pass. 

H. Piston ring dowel pin. 

I. Oiler. 

J. Exhaust connection. 

K. Grease cup. 

L. Connecting rod. 

M. Bearing cap. 

N. Drain cock. 

O. Carburetor. 

P. Throttle valve. 

Q. Check valve. 

R. Spring. 

S. Lock nut. 

T. Manifold. 

U. Lower half of crankcase. 

V. Gasket. 

AV. Air tight crankcase. 



O 




























































98 


ENGINES 


the burned gases. If the inlet port is uncov¬ 
ered at the same time as the exhaust, the 
pressure in the cylinder being greater than the 
pressure in the crankcase, will ignite the gases 
in the crankcase, causing a crankcase explo¬ 
sion. As the exhaust port is uncovered before 
the inlet port, most of the heat passes out, so 
that when the fresh gases enter the cylinder 
they are not ignited. 

Either a lean mixture or a rich mixture, 
which burn slowly, will cause a crankcase ex¬ 
plosion, because most of the gas is still burn¬ 
ing in the cylinder when the inlet by-pass is 
uncovered. Since the exhaust port does not 
close until after the inlet port closes some of 
the fresh gases entering the cylinder will 
pass out with the burning gases, which is 
another disadvantage of the two stroke cycle 
engine. 

The two port engine usually has the fuel ad¬ 
mission inlet valve in the crankcase, which is 
either automatic in its action or mechanically 
driven. The mechanically driven inlet valve 
is designed to open as the piston starts upward 
on the compression stroke, after the inlet 
by-pass has closed, admitting a fresh charge 
of fuel to the crankcase and remains open 
until top dead center or a trifle past, depending 
upon the speed of the engine. 

The three port engine does not employ an 
inlet valve. In this engine the carburetor is 
connected to a port which is covered and un¬ 
covered by the piston. As the piston goes up 
on the compression stroke in the cylinder it 
is forming a vacuum in the crankcase. This 
vacuum continues until the piston reaches a 
point about one inch before top dead center. 
Further movement of the piston uncovers the 
port to the carburetor and the vacuum formed 
in the crankcase draws in a supply of gas. This 
movement of the inrushing mixture drops off 
again as the vacuum decreases. The gas 
drawn into the crankcase has a tendency to 
condense into liquid gasoline, and if the com¬ 
pression in the crankcase is not great enough 
to force the condensed gases into the cylinder, 
the mixture will become too lean and also 
waste the fuel that is left in the crankcase. If 
too much of this condensed gas remains in the 
crankcase, the engine cannot be started. 

While considering the operation of the two 
stroke cycle engine, it is necessary to take into 
consideration the air-tight crankcase, which 
has no breather tube. As the success of the 
two stroke cycle engine depends upon the 
crankcase compression, the bearings must be 
fitted closely. If the crankcase bearings are 
worn, the mixture will be blown out through 
the bearings instead of being compressed. The 
higher this mixture is compressed in the crank¬ 


case, the better it will remain vaporized and 
the more fuel will reach the combustion cham¬ 
ber. Since it is more essential that the crank¬ 
case bearings be air tight, packing glands may 
be provided on the main bearings. 

The main bearings of the two stroke cycle 
engine are usually lubricated from grease cups, 
while the cylinders, pistons, and connecting 
rods are lubricated by oil mixed with the gaso- 



FIG. 83 


TWO STROKE CYCLE THREE PORT ENGINE 


(Left) 

A. Piston pin. 

B. Piston. 

D. Inlet port. 

E. By-pass. 

F. Exhaust port. 

G. Inlet port from 

carburetor. 

H. Crank pin. 

I. Connecting rod. 

J. Air tight crankcase. 


(Right) 

A. Piston pin. 

B. Piston. 

C. Deflector plate. 

D. Inlet port. 

E. By-pass. 

F. Exhaust port. 

G. Inlet port from 

carburetor. 

H. Crank pin. 

I. Connecting rod. 

J. Air tight crankcase. 

K. Drain cock. 


Illustration at left shows the piston on top dead cen¬ 
ter, end of the compression stroke, the bottom of the 
piston having opened the inlet port (G) to allow the 
mixture to enter the crankcase. The mixture will be 
compressed in the crankcase by the downward move¬ 
ment of the piston. 

Illustration at right shows the piston on bottom dead 
center, the burned gases passing out through exhaust 
port (F) and the compressed mixture passing from the 
crankcase through by-pass (E) and inlet port (D) into 
the cylinder. 













































































TWO STROKE CYCLE ENGINES 


99 


line. When the lubricating oil is mixed with 
the gasoline, care must be taken to keep it well 
mixed, otherwise the oil, being heavier than 
the gasoline, has a tendency to settle down in 
the bottom of the tank and may get into the 
carburetor and stop the engine. A thin or light 
grade oil should be used for this purpose. Oil 
cups are also provided in the cylinder to lubri¬ 
cate the cylinder walls. 

The speed of the ignition drive differs from 
that used on a four stroke cycle engine because 
of the difference in the number of explosions 
per revolution. A two stroke cycle engine 
fires twice as often as a four stroke cycle en¬ 
gine, consequently the ignition apparatus must 
be driven twice as fast. 

The two stroke cycle engine is more sensitive 
to a change in atmospheric conditions than the 
four stroke cycle engine, hence, the carburetor 
of the former must be adjusted more accurate¬ 
ly. Two stroke cycle engines* are not built in 
as large power units as the four stroke cycle 
type. Considerable experimenting has been 


done to eliminate crankcase compression on 
two stroke cycle engines, as this is one of its 
greatest drawbacks. 

The two stroke cycle engine operates suc¬ 
cessfully with a mixing valve, which is similar 
to a carburetor excepting that it has no fioat 
chamber to regulate the height of gasoline in 
the spray nozzle. Also, on the mixing valves 
the main air valve is adjustable. The mixing 
valve adjustments are made by means of an 
adjustable air inlet and a gasoline needle valve. 
Care must be taken not to have the gasoline 
turned on for too long a period of time before 
the engine starts as this has a tendency to 
flood the crankcase with gasoline. The mix¬ 
ing valve works very successfully on a con¬ 
stant speed engine, and as a two stroke cycle 
engine usually runs at practically a constant 
speed it will answer the purpose. The two 
stroke cycle engine is used mostly as small 
marine units and as stationary engines for 
farm use. 

Considering the four stroke cycle and two 


T.D.C. 



CYCLE OF OPERATIONS TWO STROKE CYCLE ENGINE 


























100 


ENGINES 


stroke cycle engines from a power viewpoint, 
the two stroke cycle, with its two explosions 
to one of the four stroke cycle, should give 
twice as much power, but because of the poor 
vaporization of the fuel, short inlet stroke and 
the poor scavenging of the cylinders, it does 
not develop twice the power. Should these 
faults be eliminated and the explosions be as 
powerful as those in the four stroke cycle, the 
two stroke cycle will develop nearly double 
the power, if not more, through the elimination 
of working parts. 

STARTING PRECAUTIONS 

Before trying to start an engine, after assem¬ 
bling it, always check the compression, ignition 
and fuel supply. 

If there is no compression, then as the piston 
moves down on intake, it will not form a 
sufficient vacuum to draw in the necessary 
amount of fuel. If the valves seat properly it 
is only necessary to pour a few spoonfuls of oil 
on the head of the pistons. Then spin the 
engine over a few times by hand with the igni¬ 


tion off, the pet cocks open, and the throttle 
valve closed. 

The secondary wires should be correctly con¬ 
nected to the spark plugs, according to the 
direction of rotation of the distributor brush 
and the firing order of the engine. The spark 
should occur in each cylinder when the piston 
is on top dead center compression, with the 
breaker mechanism in retard. 

See that there is gasoline at the top of the 
spray nozzle. Partly close the choke valve or 
raise the float needle valve to obtain a rich 
mixture for starting. The fuel mixture is 
then taken into the cylinder and compressed 
and the spark occurring at the right time 
should cause an explosion. If it does not ex¬ 
plode, warm the mixture by either pouring hot 
water on the inlet manifold, heating the man¬ 
ifold with a blow torch, or by removing the 
spark plugs and filling them with gasoline; 
ignite the gasolme and after it has burned out, 
screw these hot dry spark plugs into the cylin¬ 
ders and crank the engine over, priming it by 
partly closing the choke valve or by lifting the 
needle valve. 


SUMMARY 


INTERNAL COMBUSTION ENGINE 

An internal combustion engine is a me¬ 
chanical device for the changing or transform¬ 
ing of heat energy into mechanical energy. 

The two fundamental principles upon which 
the design and operation of an internal com¬ 
bustion engine depend, are: 

When a gas is compressed and its volume 
reduced, the temperature rises. 

When the temperature of a gas is increased, 
it expands. 

Types 

Two stroke cycle. 

Four stroke cycle. 

A cycle is a series of events, beginning at 
any point, completing each operation always in 
the same order and returning to the starting 
point. 

A cycle of operations in the internal com¬ 
bustion engine includes the operations neces¬ 
sary to make an engine run; namely, Intake, 
Compression, Power, and Exhaust strokes. 

A two stroke cycle engine completes a cycle 
of operations during one revolution of the 
crankshaft, two strokes of the piston, or 360° 
crankshaft travel, regardless of the number of 
cylinders. 


A four stroke cycle engine completes a cycle 
of operations during two revolutions of the 
crankshaft, four strokes of the piston, or 720° 
crankshaft travel, regardless of the number of 
cylinders. 

The automobile engine operates on the four 
stroke cycle principle. 

The average automobile engine has a ther¬ 
mal efficiency of about 11%. 

Operations 

The cycle of operations in an automobile 
engine, beginning at the inlet valve opening 
is as follows: 

The piston moves down with the inlet valve 
open and the exhaust valve closed, causing 
a vacuum within the cylinder. The throttle 
valve in the carburetor is open and there being 
a higher pressure outside than within, the air 
rushes in to fill the space formed by the down¬ 
ward movement of the piston. As the air 
rushes by the spray nozzle, it takes up a supply 
of gasoline, and due to the high air velocity, 
mixes it with the air in the form of a gasoline 
vapor. 

At the end of this, the intake stroke, the 
piston will be down and the cylinder filled with 
a mixture at approximately atmospheric pres- 






TWO STROKE CYCLE ENGINES 


101 


sure. At this point, the inlet valve closes. 
The exhaust valve remains closed and the pis¬ 
ton moves up, compressing the mixture. When 
the piston reaches its highest point of travel, 
the pressure within has been increased to about 
70 pounds per square inch. The mixture has 
been heated, dried and properly vaporized by 
this, the compression stroke. The spark occur¬ 
ring at this point ignites the mixture and as it 
burns, it explodes and expands, driving the 
piston down, with both valves closed. This is 
the power stroke. 

When the piston approaches the bottom, the 
mixture has been burned and the exhaust valve 
opening at this point allows the greater por¬ 
tion of the burned gases, which are under con¬ 
siderable pressure, to pass out. Then the 
piston moves up with the inlet valve closed 
and the exhaust valve open, forcing the re¬ 
mainder of the burned gas out of the cylin¬ 
der. When the piston reaches its highest point 
of travel, the exhaust valve closes. This ends 
the exhaust stroke and completes 720° of 
crankshaft travel. When the piston starts to 
move down, the inlet valve opens again, and 
a new mixture will be drawn in, beginning an¬ 
other cycle of operations which the engine per¬ 
forms over and over again. 

COMPRESSION 

If the compression of an engine is increased, 
the power developed increases in proportion, 
until the maximum point of compression is 
reached. 

The maximum point of compression is the 
amount of compression that an engine will 
operate under without causing pre-ignition, 
which varies on different engines. 

The average automobile engine has a com¬ 
pression of about seventy pounds per square 
inch. 

S. A. E. HORSE POWER FORMULA 


CYLINDERS 

Types 


T-shape .T-Head 

L-shape .L-Head 

Valve-in-head .I-Head 

Superimposed .F-Head 


Troubles 

Scored. 

Warped (out of round). 
Cracked w'ater jacket. 


CARBON DEPOSIT 
Cause 

Excessive or low grade lubricating oil. 

Incorrect mixture, rich, dirty or unvaporized. 

Remedy 

Kerosene. 

Water. 

Scraping. 

Burning. 

PRE-IGNITION 

Pre-ignition is a premature explosion, or the 
explosion occurring too early. 

Cause 

Advanced Spark—Spark knock. 

High Compression—Compression knock. 

Carbon Deposit—Carbon knock. 

Hot Spots—Hot engine. 

PISTONS 

Material 

Cast Iron. Semi-Steel. Aluminum Alloy. 

Design and Fitting 

The piston head must be made smaller than 
the skirt, or fitted with a greater clearance. 
Reason: It expands more, due to being in di¬ 
rect contact with the source of heat, has less 
lubrication and less opportunity of cooling. 
The piston skirt can be fitted tighter because 
it is farther away from the source of heat, has 
better lubrication and better opportunity of 
cooling, because of thinner construction. 

Three important points to consider when 
replacing pistons are: All the pistons in an 
engine should be of the same weight; all the 
pistons should be the same height from center 
of piston pin hole to head of piston; the piston 
pin holes must be at right angles to the piston 
wall. 

PISTON RINGS 
Types 

Eccentric. Concentric. One piece. Leak proof. 

Material 

Cast Iron. The three reasons for using cast 
iron in piston rings are: Its rate of expansion 
is low; it retains its elasticity better than 
other metals when heated; it is a good wear 
resisting metal. 

Clearance 

Clearance should be measured between the 
ends of the ring with a thickness gauge, when 
the ring is inside the cylinder; allow the same 
clearance as allowed on the diameter at the 








102 


ENGINES 


head of a cast iron piston of the same size. 

Back of the ring allow about 1/32", or 
enough to prevent any chance of the ring rid¬ 
ing on the bottom of ring groove. 


With the correct number of shims between 
rod and cap, pull the castle nuts as tightly 
as possible with a socket wrench of the right 
size. Then lock the nut with a cotter pin. 


PISTON PINS 
Material 

Alloy Steel—heat treated—hardened. 

Clearance 

The fitting of the piston pin in the piston is 
governed by the type of piston and engine, 
usually a tight twisting fit with palm of hand 
being correct. 


. Precaution 

When assembling an engine, always see that 
the piston pins are properly locked. 

CONNECTING RODS 
Types 

Single ^I-Beam 
Yoke [Tubular 

Bearings 

Three reasons why babbitt is used for the 
crank pin bearing of the connecting rod are; 
It has a low coefficient of expansion; it is a soft 
bearing metal (protects the crankshaft), and 
it is easy to replace and fit. 

Precautions to observe when fitting bear¬ 
ings: 

Remove all the old babbit. 

Press the new bearing into place. 

Fasten with screws or dowel pins. 

See that the dowel pins are countersunk. 

Dress the bearing flush between the rod and 
cap. 

See that the bearing does not ride on the 
fillets of the crank pin. 

Have the scraper sharp. 

Do not use long strokes. 

Do not use the point of the scraper. 

Scrape the high spots only. 

Do not fasten the rod onto the crankshaft 
too tightly. 

Each time an impression is taken, clean the 
bearing. 

Examine the crank pin for burrs or rough 
spots. 

Fasten on same crank pin and in the same 
position each time. 

When Assembling Rods in the Engine 

Clean and lubricate the bearings, pistons, 
cylinders, and crank pins. 

Lock the piston pin. 

Fasten on the same crank pin in the same 
■ position as when scraped. 


Alignment 

The crank pin and piston pin holes must be 
parallel. 

MAIN BEARINGS 
Precaution 

When fitting main bearings, scrape in the 
crankcase bearings first. 

To check the alignment of the crankshaft 
mounting, use a test indicator or surface 
gauge, and test from face of crankcase, counter 
bore, cylinder head or any machined surface. 

CRANKSHAFT 

Alignment 

To test the alignment of a crankshaft, use 
a test indicator or surface gauge while revolv¬ 
ing the shaft between lathe centers. 

Troubles 

If the crank pin bearing of the connecting 
rods are continuously wearing or working 
loose, the most probable cause is that the 
crank pin is out of round. 

If the main bearings are continuously work¬ 
ing loose, the most probable cause is that the 
crankshaft is either sprung out of alignment 
or the main journals are out of round. 


VALVES 


Poppet. 

Rotary. 

Sleeve 


(Sliding. 
] Rotary. 


Types 


Material—Poppet Valve 

Alloy steel stem, cast iron head; one piece 
alloy steel; alloy steel stem and tungsten steel 
head. 


Fitting 

When grinding valves, the two most im¬ 
portant precautions to observe are: 

Do not bear down too hard. 

Do not turn the valve continuously in one 
direction. 

When assembling the valves after grinding, 
observe the following precautions: 

Clean the valves and cylinders, remove all 
the grinding compound. 

Place the valves in the same seat in which 
they were ground. 




SUMMARY 


103 


Place the correct springs on the valves, and 
see that the springs set squarely on the re¬ 
tainers. 

The clearance of the valves in the guides 
varies on different engines. When fitting a 
new valve, the stem should have enough clear¬ 
ance in the guide to allow the valve when the 
stem is properly lubricated, to settle down 
easily against its seat, under its own weight. 

If the exhaust valve stem is too tight, it will 
stick and hold open, causing misfiring. 

The exhaust valve stem fitting too loosely, 
will not greatly affect the operation of the 
engine. 

The inlet valve stem fitting too tightly, 
causes the valve to stick and hold open, result¬ 
ing a steady continuous back-firing in the car¬ 
buretor. 

The inlet valve stem fitting too loosely, 
causes an irregular back-firing in the car¬ 
buretor, due to a lean mixture. 

VALVE CLEARANCE 

Adjust the clearance roughly to about .020". 

Run the engine until it is hot, just before 
the water boils in the cooling system. Then 
measuring with a thickness gauge, allow .002" 
clearance on the inlet and .004" clearance on 
the exhaust. This is the correct measurement 
after the lock nut is tightened. This measure¬ 
ment is made between the clearance adjusting 
nut and valve stem when the tappet is on the 
heel of the cam and the valve seated. 

TAPPETS 

Types 

Roller. Mushroom. 

VALVE SPRINGS 

The exhaust valve spring requires more ten¬ 
sion than the inlet spring, to prevent the 
exhaust valve from being forced away from its 
seat by the higher pressure in the manifold, 
during the time that there is a vacuum in the 
cylinder. 

Where both springs have the same tension, 
the inlet has an unnecessary amount of ten¬ 
sion. 

The exhaust valve spring requires enough 
tension to hold the exhaust valve against its 
seat during intake stroke. If the spring is too 
weak, misfiring will result. 

The inlet valve spring requires enough ten¬ 
sion to cause the valve stem and tappet to 
follow the contour of the cam to insure the 
valve closing at the proper time. 

CAMSHAFT 

The purpose of the camshaft and cams is to 
operate the valves. 


The toe of the cam governs the lift of the 
valve, the length of the stroke, and the speed 
of the individual valve opening and closing. 

The order in which the cams are set on the 
camshaft and the type of crankshaft governs 
the firing order of the engine. 

To determine the angles at which the cams 
are set on the camshaft, divide the angle the 
crankshaft travels between the explosions, by 
two. 

The camshaft always revolves one-half 
crankshaft speed in all four stroke cycle en¬ 
gines. 

In engines of conventional design, the cam¬ 
shaft timing gear always has twice as many 
teeth as the crankshaft or master gear. 

VALVE OPENINGS AND CLOSINGS 

T. D. C. means TOP DEAD CENTER. 

B. D. C. means BOTTOM DEAD CENTER. 

Valve openings and closings are considered 
in degrees of crankshaft travel. 

F. P. Firing point is T. D. C. at‘the end of 
compression stroke. 

E. C. Exhaust valve closing. 

E. O. Exhaust valve opening. 

I. O. Inlet valve opening. 

I. C. Inlet valve closing. 

The following operations are based on the 
average engines: 

E. C.— 5° past T. D. C. 

E. 0.-135° past T. D. C. 

E. 0.-135° past F. P. 

E. O.— 45° before B. D. C. 

I. C.— 35° past B. D. C. 

I. C.—145° before T. D. C. 

I. O.— 10° past T. D. C. 

I. 0.-350° before F. P. 

The average length of the different strokes: 


Intake . 205° 

Compression . 145° 

Power. 135° 

Exhaust.. . 230° 

Lap. 5° 


One cycle of operation. .. . 720° 


INLET MANIFOLD 

A leak in the inlet manifold will cause an 
irregular back-firing in the carburetor, due to 
a lean mixture. 

EXHAUST MANIFOLD 

If the exhaust manifold is too small it will 
cause a loss of power, over-heating of the en¬ 
gine and possibly misfiring, due to the back 
pressure in the manifold. 

An explosion in the exhaust manifold or 
muffler is usually caused by misfiring. 










104 


ENGINES 


FOUR CYLINDER ENGINE 
Four Stroke Cycle 

A four cylinder engine fires every 180®. An 
inlet valve opens every 180° crankshaft travel, 
as also does an exhaust valve. The respec¬ 
tive valves open every 90° camshaft travel. All 
inlet cams are set on the camshaft 90° apart; 
exhaust cams same. There are only two pos¬ 
sible firing orders and they are both standard. 

Four Cylinder Standard Firing Orders 

1-2-4-3 

1-3-4-2 

In a four cylinder engine with a power stroke 
of 135°, after the completion of one power 
stroke, there is 45° crankshaft travel before 
the next one fires. During every 180° of crank¬ 
shaft travel, there is an interval of 45° without 
power. This gives a total of 180° without 
power during the time required to complete 
a cycle of operations, or 720° crankshaft 
travel. When one cylinder misfires, the angle 
traveled by the crankshaft between explosions 
is 360°. During this time only one power 
impulse occurs, which results in 225° travel 
without power. 

SIX CYLINDER ENGINE 

A six cylinder engine fires every 120°. An 
inlet valve opens every 120° crankshaft travel, 
as also does an exhaust valve. The respec¬ 
tive valves open every 60° camshaft travel. 
All inlet cams are set on the camshaft 60° 
apart; exhaust cams same. There are eight 
possible six cylinder firing orders. 

Six Cylinder Standard Firing Orders 

1-5-3-6-2-4 

1-4-2-6-3-5 

In a six cylinder engine with a 135° power 
stroke, 15° before the end of one power stroke, 
another begins. Every 120° of crankshaft 
travel there is an interval of 15° during which 
there are two cylinders on power. During two 
revolutions of the crankshaft or the time re¬ 
quired to complete one cycle of operations, 
there are six different intervals of 15° each, or 
a total of 90° crankshaft travel with two cyl¬ 
inders on power at the same time. If one 
cylinder misfires there will be an interval 
of 240° from the time one cylinder fires until 
another cylinder fires, thus 240°—135° gives 
105° without power. 

EIGHT CYLINDER V TYPE ENGINE 

A standard eight cylinder V-type engine fires 
every 90°. An inlet valve opens every 90° of 
crankshaft travel, as also does an exhaust 


valve. The respective valves open every 45° of 
camshaft travel. All inlet cams are set on the 
camshaft 45° apart; exhaust cams same. 
Since an eight cylinder V type engine is the 
same as two four cylinder engines using the 
same camshaft and crankshaft, each engine 
block will have a standard four cylinder firing 
order. There are four possible eight cylinder 
firing orders. 

Eight Cylinder Standard Firing Orders 

1R-4L-2R-3L-4R-1L-3R-2L 

1R-4L-3R-2L-4R-1L-2R-3L 

In an eight cylinder V-type engine with a 
135° power stroke, 45° before the end of one 
power stroke, another begins. Every 90° of 
crankshaft travel there is an interval of 45° 
during which there are two cylinders on power. 
During the time required to complete a cycle 
of operations, or two revolutions, there are 
eight intervals of 45° each, or a total of 360°, 
or one-half the time there are two cylinders 
on power at the same time. 

If one cylinder misfires, from the time that 
one fires until another fires, is 180°—135° 
which gives an interval of only 45° without 
power. 

TWELVE CYLINDER V TYPE ENGINE 

A standard twelve cylinder V type engine 
fires every 60°. An inlet valve opens every 60° 
of crankshaft travel, as also does an exhaust 
valve. The respective valves open every 30° 
of camshaft travel. All inlet cams are set on 
the camshaft 30° apart; exhaust cams same. 
There are eight possible twelve cylinder firing 
orders. 

Twelve Cylinder Standard Firing Orders 

1R-6L-5R-2L-3R-4L-6R-1L-2R-5L-4R-3L 

1R-6L-4R-3L-2R-5L-6R-1L-3R-4L-5R-2L 

In a twelve cylinder engine with a 135° 
power stroke, 60° after the beginning of one 
power stroke, another begins, 60° later an¬ 
other, etc. Since the third one begins 15° be¬ 
fore the first one ends its power stroke, then 
there are two cylinders on power all the time, 
and during 15° of the crankshaft travel there 
are three cylinders on power at the same time. 
Thus during a cycle of operations in a twelve 
cylinder engine, there is a total of 720° that 
two cylinders are on power, and 180° of the 
720°, that three cylinders are on power at the 
same time. When one cylinder misfires, from 
the time one cylinder fires until another fires 
is 120°; at the end of 120° crankshaft travel, 
the first one still has 15° to travel on power, so 
that there is always continuous power in a 
twelve cylinder engine even when one cylinder 
misfires. 



105 


SUMMARY 


COOLING SYSTEMS 


Types 


Air cooled. 
Water cooled 


(Thermo-syphon. 
iCirculating pump. 


LUBRICATION 

The three most important purposes of lubri¬ 
cation, are: 

General lubrication, compression seal and 
cooling. 

OIL PUMPS 

The capacity of a gear type pump depends 
upon: 

The speed, the size and fit of the gears, the 
number and size of the teeth, the grade of oil, 
and the type of lubricating system. 

The capacity of a plunger pump depends 
upon: 

The speed, the stroke, the bore, the size of 
the inlet and outlet pipes, the grade of oil, and 
the type of lubricating system. 

FUEL SYSTEMS 
Types 

Gravity—(The tank must have an air vent.) 

Vacuum—(The tank must have an air vent.) 

Pressure—(The tank must not have an air 
vent.) 

CARBURETION 

Definitions 

The carburetor is a mechanical device for 
the mixing of fuel and air into a vapor of 
different proportions as may be required by 
the engine. 

The purpose of the fioat and float valve is 
to regulate the fuel supply in the float chamber 
and jets, maintaining a constant level just be¬ 
low the top of spray nozzle. 

The purpose of the venturi tube is to restrict 
the air passage, thus increasing the velocity of 
the air at the spray nozzle. 

The purpose of the throttle valve is to con¬ 
trol the speed of the engine by regulating the 
amount of mixture which is taken into the 
cylinder. 

The purpose of the choke valve is to vary the 
size of the main air inlet, to regulate the mix¬ 
ture while starting. This should be used only 
while starting or until the engine warms up. 

The purpose of the auxiliary air valve is to 
admit air into the mixing chamber above the 
spray nozzle when the engine is running at 
high speed. This prevents the mixture from 
becoming too rich at high speeds. 

The purpose of the stop screw is to keep the 
throttle valve from closing completely when 
the throttle valve control lever is in closed 


position, thus preventing the engine from 
stopping. 

Misfiring at idling speed, an irregular back¬ 
firing at normal speed, high speed, or upon 
acceleration, indicates a lean mixture. 

A galloping or loping of the engine, running 
irregularly but still firing all cylinders, black 
smoke issuing from the exhaust, is an indica¬ 
tion of a rich mixture. 

If the mixture is too rich the engine will mis¬ 
fire, but a rich mixture will not cause a back¬ 
fire. 

Blue smoke issuing from the exhaust is an 
indication of the burning of lubricating oil in 
the combustion chamber. 

Troubles 

A leaky carburetor may be caused by a loose 
connection, flaw or sand hole in the casting, 
float punctured, or gasoline logged, or stuck 
down, float valve sprung or seat rough, sedi¬ 
ment under the float valve, float lever arms 
bent (upward), or anything which may prevent 
the float valve from seating properly when the 
gasoline reaches the correct level. 

A starvation of the carburetor (lack of gaso¬ 
line) may be caused by anything that prevents 
the flow of gasoline to the spray nozzle as fast 
as the engine consumes it. This may be caused 
by not having an air vent in the gasoline tank 
(gravity or vacuum), a leak in the gasoline 
tank or line, loss of pressure (pressure sys¬ 
tem), insufficient amount of gasoline supplied 
by the vacuum tank, an obstruction anywhere 
in the supply line, sediment, screens dirty or 
rusty, float lever arms bent (down), float stuck 
(up), gasoline or fuel adjusting valve adjusted 
too close, sediment or obstruction in the jets or 
spray nozzle. 

TESTING COMPRESSION 

To test the compression, remove the spark 
plug and screw a pressure gauge in the spark 
plug hole. As the engine is cranked over 
slowly, this will register the number of pounds 
pressure per square inch in the cylinder. 

To determine the weak from the strong cyl¬ 
inder, where a pressure gauge is not available, 
open all pet cocks but one, crank the engine 
over and feel the compression by the resistance 
of the crank and the rebound of the piston over 
T. D. C., remembering that tight bearings, tight 
pistons, or dry cylinder walls offer resistance, 
but not a rebound or recoil. 

ASSEMBLING AND STARTING AN 
ENGINE 

When assembling an engine, always clean 
and lubricate all bearing surfaces and examine 
the crankcase surface, the oil pan, the cylinder 
flange, the cylinder head, the manifold flanges. 




106 


ENGINES 


and every point where one machined surface 
comes in contact with another and see that 
there are no nicks, or rough places. Use an 
oil stone to remove these uneven places on 
the machined surfaces. If the surfaces are 
even and a good gasket is used, there is no 
necessity for using shellac. Place lubricating 
oil or cup grease on each side of gasket in¬ 
stead. This prevents tearing or destruction of 
the gasket when the part is removed. 

Always use a wrench (a socket wrench 
if possible) of the correct size when removing 
or tightening a nut. Never use pliers or a cold 
chisel. 

Always lock a nut where there is a means of 
locking provided, such as a lock washer, safety 
wire or cotter pin. 

When adjusting a carburetor, always adjust 
to the operating condition of the engine, that 
is, make the adjustment when the engine is hot 
and running under load. Low speed adjust¬ 
ment should be made when the engine is run¬ 
ning slowly, under load, and with retarded 
spark. High speed adjustment should be made 
when the engine is running at high speed, 
under load and with an advanced spark. 

Three things that are necessary to start an 
engine that is properly assembled are: Com¬ 
pression, spark occurring at the correct time, 
and fuel in the engine. 

TWO STROKE CYCLE 

In a two stroke cycle engine, regardless of 
the number of cylinders, all cylinders fire dur¬ 
ing one revolution of the crankshaft, two 
strokes of the piston or 360° .of crankshaft 
travel. 

Every time a piston reaches T. D. C. it is on 
the firing point. 

To determine the number of degrees the 
crankshaft turns between explosions, divide 
360° (the time required to fire all cylinders) 
by the number of cylinders. 

The angle at which the crank throws are 
set is the same as the angle traveled by the 
crankshaft between explosions. 


DON’TS 

Don’t race an engine with the clutch dis¬ 
engaged. 

Don’t run a new car, or an old car that has 
just been repaired, at high speed until the parts 
are worn in. 

Don’t pour cold water in the cooling system 
when the engine is hot and the water has evap¬ 
orated; wait until the engine cools. 

Don’t run the engine without proper means 
of cooling and lubrication. 

Don’t tighten the packing nuts on water 
and oil pumps too tightly; just tight enough to 
stop the leak is all that is necessary. 

Don’t use any kind of oil for lubrication ex¬ 
cept the best; there is no oil just as good as 
the correct oil. 

Don’t try to adjust the carburetor every day 
to suit varying atmospheric conditions. Per¬ 
haps it will be correct the next day. 

Don’t use the choke valve for stopping an 
engine. 

Don’t prime an engine by squirting gasoline 
into the cylinder through a petcock. Partly 
close the choke valve or raise the needle valve. 

Don’t use the choke valve any more than is 
absolutely necessary. 

Don’t keep spinning an engine. When it 
will not start, check up the compression, mix¬ 
ture and ignition. 

Don’t overload an engine. If the engine be¬ 
gins to labor, shift to a lower speed. 

Don’t take chances. Know that you are 
right and then go ahead. 

Don’t depend upon the other fellow. Have 
confidence in yourself. 

Don’t tell the other fellow what you can do— 
show him. 

Don’t feel discouraged if you make a mis¬ 
take. If you never make the same mistake 
again, you are improving. 

Don’t mind ridicule; every big man is ridi¬ 
culed sometime in life. 

Don’t copy. Be original. 

Don’t watch the clock. Watch your work. 

THINK! 



ENGINES 


107 


QUESTIONS 


1— What is an internal combustion engine? 

2— Name the types of internal combustion 
engines. 

3— Explain the operation of each type. 

4— What is a cycle? 

5— What is a cycle of operations of an en¬ 
gine? 

6— How many events occur in a complete 
cycle of operations? 

7— How many degrees crankshaft travel are 
necessary to complete a cycle of operations in 
a four cylinder, four stroke cycle engine? 

8— How many degrees crankshaft travel are 
necessary to complete a cycle of operations in 
a six cylinder, two stroke cycle engine? 

9 (a)—How many revolutions of the crank¬ 
shaft are necessary to complete a cycle of 
operations in an eight cylinder, V type engine, 
where the crank throws are set 180° apart, and 
the cylinders 90° apart? 

(b)—How many degrees will the camshaft 
revolve while the above engine is completing 
a cycle of operations? 

10— How many degrees crankshaft travel 
are necessary to complete a mechanical cycle? 

11— On the average engine where does the 
exhaust valve open and close? 

12— Where does the inlet valve open and 
close? 

13— What is the length in degrees of each 
stroke? 

14— Which is the longest and which is the 
shortest stroke of the cycle? 

15— What determines the inlet valve clos¬ 
ing point on any engine? 

16— Why is the inlet valve allowed to re¬ 
main open past B. D. C.? 

17— What prevents the mixture from being 
forced out when the piston moves upward be¬ 
fore the inlet valve closes? 

18— Why is the exhaust valve opened before 
B. D. C.? 

19— What causes the burned gases to pass 
out when the piston is moving downward with 
the exhaust valve open? 

20— Why is the exhaust valve allowed to re¬ 
main open past T. D. C.? 

21— What is the purpose of the lap between 
the closing of the exhaust and the opening of 
the inlet valves? 

22— Name the types of cylinder castings. 

23— What does the name refer to? 

24— What materials are used in cylinder con¬ 
struction? 

25— Give the advantages and disadvantages 
of the different types of cylinders. 


26— Name the most common cylinder 
troubles. 

27— How should a scored cylinder be re¬ 
paired? 

28— How would a cylinder be repaired that 
is out of round? 

29— How would a cracked water jacket (a 
small crack) be repaired? 

30— How would a cracked water jacket (a 
large crack) be repaired? 

31— Explain how to lap in a cylinder after 
reboring. 

32— Explain how to fit a new oversize piston 
after the cylinder has been rebored. 

33— Should the rings be removed from the 
piston when lapping? 

34— What precautions should be observed 
when assembling an engine after the piston 
and cylinders have been lapped in? 

35— What are the two main causes of car¬ 
bon deposit? 

36— What effect will carbon deposit have on 
the operation of an engine? 

37— Why does carbon deposit cause a 
knock? 

38— Name and explain three common meth¬ 
ods for removing carbon deposit. 

39— Name three probable causes of pre-igni¬ 
tion. 

40— Will the spark advanced too far affect 
the running of the engine? How? 

41— How will excessive compression affect 
the operation of an engine? 

42— At what speed will a compression knock 
be more noticeable? 

43— How would a compression knock be 
remedied? 

44— If the compression of an engine is low¬ 
ered, will there be an increase or decrease in 
power at normal running speed? 

45— If two engines of the same model and 
size with one running light and the other under 
load at the same speed, which engine is de¬ 
veloping the more power? Which one has the 
more compression? Why? 

46^—If one of the engines has forty pounds 
compression and the other has sixty pounds, 
which will develop the more power? Why? 

47— The same two engines at the same 
speed, the same load and with equal compres¬ 
sion; the water in the cooling system of one 
has a temperature of 200° F. and the other 
120° F. Which engine has the higher effi¬ 
ciency? Why? 

48— What are the two fundamental princi¬ 
ples that govern the design and operation of 
an internal combustion engine? 



108 


ENGINES 


49— What is meant by the H. P. of an en¬ 
gine? 

50— What is meant by the piston displace¬ 
ment of an engine? 

51— What is meant by the R. P. M. of an 
engine? 

52— What is meant by the piston speed of 
an engine? 

53— What is meant by the M. E. P. of an 
engine? 

54— What is meant by the B. H. P. and 1. H. 
P. of an engine? 

55— What is the 1. H. P. of a four cylinder, 
four stroke cycle engine with a 4" bore and a 
5" stroke, with an M. E. P. of 90 lbs. per sq. in. 
developing its maximum torque or power at 
2,500 R. P. M.? 

56^—What is the piston speed of the above 
engine expressed in ft. per min.? 

57— What is the total piston displacement of 
the above engine? 

58— Suppose it is desired to determine the H. 
P. of a six cylinder engine and no data or speci¬ 
fications of the engine are available except 
that the inside diameter of the cylinder is 
3-1/2". What would be the approximate 
H. P.? 

60— Give three reasons why the skirt of a 
piston may be fitted tighter, allowing less clear¬ 
ance than at the top. 

61— What materials are used in piston con¬ 
struction? 

62— On the average water cooled engine, 
what are the correct clearances to allow on a 
cast iron piston of three inch diameter, meas¬ 
ured on the diameter above the top ring and 
at the lower skirt? A 31 / 2 " piston? A 4" 
piston? 

63— How much clearance should be allowed 
on the head and skirt of an aluminum alloy 
piston of 3", 31 / 2 ". 4" diameters respectively? 

64— When fitting piston rings, how much 
clearance should be allowed back of the ring, 
that is, between the inside diameter of the 
ring and the outside diameter of the bottom 
of ring groove, when the outside surface of 
the ring is fiush with the outside surface of the 
piston? 

65— How tight should the rings be fitted into 
the ring groove on the average piston? 

66— What is the correct clearance to allow 
between the ends or joint of a 4" diameter 
ring? 

67— What is the proper way to measure the 
clearance between the ends of a ring? 

68— Why is cast iron generally used in piston 
ring construction? 

69— If all the pistons in the engine do not 
weigh the same, how would this affect the 
running of the engine? 

70— When the pistons in the engine are not 


all of the same height or distance from the 
center line of the piston pin hole to the head 
of the piston, how will this affect the operation 
of the engine? 

71— What is the common method used for 
fitting piston pins? 

72— How tight should the piston pin be fitted 
on the average engine? 

73— What is the purpose of a connecting 
rod? 

74— Why is the crank pin bearing usually 
made of babbitt? 

75— What are the main precautions to ob¬ 
serve when fitting bearings? 

76— When taking an impression, how tight 
should the bearing be on the shaft? 

77— When fitting the bearings in the engine, 
what precautions should be observed? 

78— —When assembling the rods, how many 
shims should be used? How tight should the 
bearings be fitted? 

79— After the castle nuts are on the connect¬ 
ing rod bolts and are pulled up tight, if the cot¬ 
ter pin hole is not in line, would it be advisable 
to loosen up on the nut in order to insert cotter 
pin? Would it be advisable to let the nut re¬ 
main tight at that point and not insert a cotter 
pin? 

80— How is the alignment of a connecting 
rod checked? Of a crankshaft? 

81— Besides the precautions used in fitting 
connecting rod bearings, what other precau¬ 
tion must be observed when fitting the main 
bearings? 

82— Is there a thrust bearing on the crank¬ 
shaft? 

83— Is the thrust bearing adjustable? 

84— How much end play should be allowed 
in the crankshaft? 

85— How will excessive end play of the 
crankshaft affect the running of the engine? 

86— What method is used to test for a loose 
connecting rod bearing? Main bearing? 

87— If the crank pin bearings of the con¬ 
necting rods are continuously working loose, 
what is the most probable cause? 

88— If the main bearings of the crankshaft 
are continuously working loose, what is the 
most probable cause? 

89— Explain how to pour a connecting rod 
bearing. 

90— Explain how to fit a yoke type connect¬ 
ing rod. 

91— What precautions should be observed 
when the crank shaft is to remain out of the 
engine for some time? 

92— What materials are used in valve con¬ 
struction? 

93— Name the different types of valves. 

94— What precautions should be observed 
when grinding valves? 



ENGINES 


109 


95— What precautions should be observed 
when assembling valves and springs? 

96— Which valve requires the stronger 
spring and why? 

97— How strong should an exhaust valve 
spring be? 

98— How strong should an inlet valve spring 
be? 

99— How is the accurracy of a valve stem 
checked? 

100— Under normal conditions, is it advis¬ 
able to reface a valve? 

101— If the exhaust valve stem is fitted too 
tightly, how will it affect the operation of the 
engine? 

102— If the exhaust valve stem is fitted too 
loosely, how will it affect the operation of the 
engine? 

103— If the inlet valve stem is fitted too 
tightly, how will it affect the operation of the 
engine? 

104— If the inlet valve stem is fitted too 
loosely, how will it affect the running of the 
engine? 

105— How much clearance should be allowed 
on the exhaust valve measured with a thick¬ 
ness gauge between the clearance adjusting 
screw and valve stem, when the engine is hot? 

106— What precautions should be observed 
when making this adjustment? 

107— How will excessive clearance affect the 
valve operation? 

108— How will excessive clearance affect the 
engine operation? 

109— How will insufficient clearance on the 
exhaust valve affect the engine operation? 

110— How will insufficient clearance on the 
inlet valve affect the engine operation? 

111— Name the different types of tappets 
with the advantages and disadvantages of 
each. 

112— How tight should the tappets be fitted 
in their guide? 

113— What is the purpose of a camshaft? 

114— What is the purpose of the toe on the 
cam? 

115— What part of the engine operation is 
governed by the toe on the cam? 

116— What is governed by the order in which 
the cams are set on the camshaft? 

117— How many degrees apart on the cam¬ 
shaft are the inlet cams set on a four, six, 
eight and twelve cylinder engine respectively? 

118— How many degrees apart on the cam¬ 
shaft are the exhaust cams set on a four, six, 
eight and twelve cylinder engine respectively? 

119— On a four cylinder T-head engine with 
a firing order of 1-2-4-3, how many degrees 
apart on the camshaft are No. 1 and No. 2 
inlet cams set? How many degrees apart are 
Nos. 1 and 4 exhaust cams set? 


120— On a twelve cylinder V type engine, 
crank throws set 120°, cylinders set 60°, with a 
firing order that starts 1R-6L-5R, how many 
degrees apart will Nos. IR and 3R cylinders 
fire? How many degrees apart crankshaft 
travel will Nos. IR and 3R inlet valves open? 
How many degrees apart camshaft travel will 
Nos. IR and 3R inlet valves open? How many 
degrees apart on the camshaft are Nos. IR and 
3R inlet cams set? 

121— What determines the distance apart the 
valves open, camshaft travel? 

122— What determines the distance apart 
that the cams are set on the camshaft? 

123— What governs the capacity of a gear oil 
pump? 

124— What governs the capacity of a plung¬ 
er oil pump? 

125— How tight should the packing nut be 
adjusted on any pump? 

126— What is the purpose of this packing? 

127— How will a leak in the inlet manifold 
affect the operation of the engine? 

128— How would you test for a leak in the 
inlet manifold? 

129— What three things determine the dis¬ 
tance apart the explosions occur? 

130— How many degrees apart do the ex¬ 
plosions occur in a four, six, eight and twelve 
cylinder engine respectively? 

131— How many possible four cylinder fir¬ 
ing orders are there? 

132a—Name the standard four cylinder fir¬ 
ing orders. 

132b—With the cylinder head removed, how 
would No. 1 piston be placed on T. D. C. at 
the end of compression? How would the fir¬ 
ing order be determined? How would the 
camshaft be timed? 

133— With a firing order of 1-2-4-3, with No. 
1 on the firing point, on what strokes would 
Nos. 2, 3 and 4 be? 

134— When the inlet valve starts to open 
in No. 2, on what stroke will No. 3 be? 

135— When the exhaust valve closes in No. 
4, on what stroke will No. 1 be? 

136— When the exhaust valve starts to open 
in No. 2, on what stroke will No. 3 be? No. 4? 

137— If the camshaft gear has sixty teeth, 
how many teeth will there be in the crankshaft 
or master gear? 

138— While the engine is completing a cycle 
of operations, how many degrees will the cam¬ 
shaft revolve? 

139— How many degrees does the crankshaft 
of a four cylinder engine travel without power 
delivered from the piston, during the time re¬ 
quired to complete a cycle of operations and 
how many cylinders will fire? 

140— How many possible six cylinder firing 
orders? 



110 


ENGINES 


141— Name the two standard six cylinder 
firing orders. 

142— Explain how to time a six cylinder en¬ 
gine when the flywheel is not marked. 

143— Explain how to adjust the valve clear¬ 
ance on a six cylinder engine. 

144— With a firing order that starts 1-5, how 
many degrees apart will Nos. 1 and 6 fire? How 
many degrees apart on the camshaft will Nos. 
6 and 2 exhaust cams be set? 

145— With a firing order that starts 1-4, 
when No. 1 is firing, on what strokes will Nos. 
2, 3, 4, 5 and 6 be? 

146— When the exhaust valve is opening in 
No. 2, on what stroke will No. 6 be? No. 5? 

147— When the inlet valve is closing in No. 5, 
on what stroke will No. 6 be? No. 2? 

148— When one cylinder misfires, how many 
degrees does the crankshaft of a six cylinder 
engine revolve without power? 

149— On a six cylinder engine, how many 
degrees are there with two cylinders on 
power at the same time, during 720° crank¬ 
shaft travel? 

150— How many possible eight cylinder fir¬ 
ing orders? 

151— Name the two most used eight cylinder 
firing orders? 

152— How would the firing order of an eight 
cylinder engine be determined? 

153— Explain how to time the camshaft on 
an eight cylinder engine. 

154— With a firing order that starts 1R-4L- 
2R, how many degrees apart will Nos. 2R and 
4R cylinders fire? How many degrees apart 
will Nos. IL and 2L inlet valves open, crank¬ 
shaft travel? Camshaft travel? How many 
degrees apart on the camshaft will Nos. 2R and 
IL exhaust cams be set? 

155— With a firing order that starts 1R-4L- 
3R, when the inlet valve is closing in No. 2R, 
on what stroke is No. 3R? When the exhaust 
valve is opening in No. 3L, on what stroke is 
No. 4R? 

156— If one cylinder in an eight cylinder en¬ 
gine misfires, how many degrees does the 
crankshaft revolve without power? 

157— If the secondary cables are removed 
from the right bank of an eight cylinder engine 
firing 1R-4L-3R, etc., what will be the firing 
order of the left bank and how many degrees 
apart will the explosions occur? 

158— How many possible twelve cylinder fir¬ 
ing orders? 

159— Name the two standard twelve cylinder 
firing orders. 

160— In a twelve cylinder engine, how many 
revolutions of the crankshaft are required to 
complete a cycle of operations? 

161— How many degrees crankshaft travel 


are required to fire all cylinders of a twelve 
cylinder engine? 

162— With a firing order that starts 1R-6L- 
5R, how many degrees will the camshaft travel 
from the time No. IR inlet valve opens until 
it again opens? 

163— With the above firing order, how many 
degrees apart, crankshaft travel, will Nos. 2L 
and 6R cylinders fire? 

164— How many degrees apart camshaft 
travel will Nos. IL and 4R inlet valves open? 
How many degrees apart will Nos. IL and 4R 
exhaust cams be set on the camshaft? 

165— When No. 5R exhaust valve is just 
closing, what cylinder will be on the firing 
point? 

166'—When the inlet valve just starts to 
open in No. IL, to what cylinder should the ig¬ 
nition be timed, with the breaker mechanism 
in full retard? 

167— When the inlet valve is closing in No. 
6 R, on what stroke will No. IR be? No. 2R? 

168— With a firing order that starts 1R-6L- 
4R, when the exhaust valve is just opening 
in No. 3R, on what stroke is No. 4R? 

169— What piston is on T. D. C. at the same 
time as No. 2L? 

170— In an eight cylinder engine, when 
there are two pistons on T. D. C. in one bank, 
how many will be on B. D. C. in the other bank 
at the same time? In the same bank? 

171— In a six cylinder, when there are two 
pistons on T. D. C., how many will be on B. D. 
C. at the same time? 

172— What is the standard setting in degrees 
of the cylinders on eight and twelve cylinder 
engines? 

173— What is the standard setting in degrees 
of the crank throws on four, six, eight and 
twelve cylinder crankshafts respectively? 

174— In a standard twelve cylinder engine, 
when there are two pistons on B. D. C. in one 
bank, how many pistons are on T. D. C. in the 
other bank? 

175— When one cylinder misfires in a twelve 
cylinder engine, how many degrees does the 
crankshaft travel without power? 

176— What is the test for a misfiring cylinder 
in an eight cylinder engine? In a twelve cyl¬ 
inder engine? 

177— How is it possible to determine if No. 
2R is firing? 

178— How would No. 2R be placed on T. D. 
C. compression in a twelve cylinder engine? 

179— Explain how to place No. IR on T. D. 
C. compression in an eight cylinder engine. 

180— Give some of the advantages and dis¬ 
advantages of a sleeve valve engine? 

181— What method is used to determine the 
firing order of a sleeve valve engine? 




ENGINES 


111 


182— How would the eccentric shaft be 
timed in a six cylinder sleeve valve engine? 

183— Name the types of fuel systems. 

184— Should there be an air vent in the gas¬ 
oline tank of the gravity fuel system? 

185— If this air vent should become stopped 
up, would the operation of the engine be af¬ 
fected? How? 

186— In a pressure system, what are the 
results if there is a greater pressure than five 
pounds in the tank and gasoline line? 

187— Explain the action of the vacuum fuel 
system. 

188— What is the purpose of the lower cham¬ 
ber of the vacuum tank? 

189— What is the purpose of the vacuum or 
suction valve? 

190— If the fioat should become punctured, 
what would be the result? 

191— If the air valve does not seat properly, 
what is the result? 

192— If the gasoline is coming out of the air 
vent at the top of tank, what is the most prob¬ 
able cause? 

193— Why will a vacuum system starve the 
carburetor at high engine speeds? 

194— Name the different cooling systems. 

195— Give some of the advantages and dis¬ 
advantages of an air cooled engine. 

196— Why is it possible to obtain more miles 
per gallon of fuel from an air cooled engine 
than from a water cooled engine? 

197— What causes the water to circulate in 
a thermo-syphon cooling system? 

198— What governs the temperature re¬ 
quired to start a circulation? 

199— Explain the different ways of regulat¬ 
ing the temperature in a circulating system. 

200— Explain how to remove the scale from 
the cooling system. 

201— What causes this scale to form? 

202— What is the best prevention of the 
scale forming? 

203— How will this scale in the cooling sys¬ 
tem affect the operation of an engine? 

204— What are the three most important 
purposes of lubrication? 

205— What governs the grade of oil to be 
used in an engine? 

206— How can the correct grade of oil for 
an engine be determined? 

207— What precaution should be observed 
when buying lubricating oil? 

208— What is the correct amount of oil to 
use in the engine? 

209— How can the correct amount of oil be 
determined? 

210— Why is it necessary to drain the old oil. 
and replace with new oil? 

211— How often should this be done? 


212— What is the advantage of washing the 
engine with kerosene? 

213— What precaution should be observed 
when washing the engine with kerosene? 

214— Why does the average engine demand 
a heavier oil in summer than in winter? 

215— Give a brief explanation of the different 
lubricating systems. 

216— What is the purpose of a carburetor? 

217— What is the purpose of the fioat and 
float needle valve? 

218— What is the purpose of the gasoline 
adjusting valve? 

219— What is the purpose of the choke 
valve ? 

220— When should the choke valve be used? 

221— What is the purpose of the throttle 
valve? 

222— What is the purpose of the auxiliary 
air valve? 

223— What is the purpose of the stop screw? 

224— Where is the auxiliary air valve lo¬ 
cated? 

225— How many valves are used in the aver¬ 
age carburetor? 

226— What is the purpose of the venturi 
tube? 

227— Is the stop screw adjustable? 

228— What is meant by the term “gasoline 
level”? 

229— Name some of the causes of a leaky 
carburetor. 

230— What is meant by the term “starvation 
of the carburetor”? 

231— Why does the engine demand a richer 
mixture when starting? 

232— Why does the mixture grow richer at 
high speeds? 

233— What determines when the mixture is 
too lean? 

234— How will a rich mixture affect the 
operation of the engine? 

235— What does a blue smoke from the ex¬ 
haust indicate? 

236— What will cause a black smoke to issue 
from the exhaust? 

237— What does an irregular backfiring in 
the carburetor indicate? 

238— Will a lean mixture cause a backfire 
at idling speeds? 

239— If the engine backfires in the carbure¬ 
tor when starting, is that an indication of a 
lean mixture? 

240— Why will a leak in the inlet manifold 
cause a backfire in the carburetor? 

241— Why is this more noticeable at low 
speeds? 

242— What will cause a regular continuous 
backfiring in the carburetor? 

243— What is the correct way to obtain the 
correct mixture for starting? 



112 


ENGINES 


244— Can a carburetor be adjusted to give 
the correct mixture under all conditions? 

245 — Under what conditions should the high 
speed adjustments be made? 

246 — Should the low speed adjustment be 
made with the clutch engaged or disengaged? 

247— How will a leaky float affect the car¬ 
buretor action? 

248— If the float valve does not seat proper¬ 
ly, will the carburetor action be affected? 

’ 249 —What will be the result if the engine 
is stopped by closing the choke valve? 

250— Why is the float valve sometimes 
raised when starting the engine? 

251 — Explain the operation of a one cylinder, 
two port, two stroke cycle engine. 

252— What is the average length of the 
power stroke; the exhaust stroke? 

253 — How is it possible to tell when piston 
is on T. D. C.? 

254— In a four cylinder two cycle engine, 
how many degrees apart do the cylinders Are? 

255— In a six cylinder engine how many de¬ 
grees apart are the crank throws set? 

256— What is the purpose of the deflector 
plate? 

257— If there is unequal compression in the 
different cylinders of an engine, how is it pos¬ 
sible to determine the weak ones? 

258— When driving in low at low speed, the 


engine runs well; when driving in high at high 
speed, it runs well, but if the engine is throt¬ 
tled down to a hard pull in high, it lopes, vi¬ 
brates, runs irregularly; what is the trouble? 

259_what three things are necessary to 
start an engine that is properly assembled? 

260— If when trying to start an engine only 
one cylinder fires, what is the cause and 
remedy? 

261— If the engine is wired wrong according 
to the firing order, how will the engine opera¬ 
tion be affected? 

262— Name some of the more important pre¬ 
cautions to observe when assembling an en¬ 
gine. 

263— Is it advisable to try to eliminate back¬ 
firing in the carburetor upon acceleration? 

264— If when driving at high speeds, the foot 
should slip off the accelerator, allowing the 
throttle valve to close suddenly, you notice a 
misfiring; what is the cause? Is it advisable 
to try to remedy this? 

265— Is it advisable to use the compression 
of the engine as a brake? What precautions 
should be observed? 

266— When stopping the engine, which is the 
better, to close the throttle valve first or cut 
off the ignition? Why? 

267— If after cutting off the ignition, the en¬ 
gine still runs, what is the trouble? 





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ENGINES 


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TOOLS 


SCREW DRIVERS 

The screw driver is a tool, much like a blunt 
chisel in form, which is inserted in the slotted 
heads of screws, to turn them for inserting or 
removing. It is usually made of drill rod or 
high carbon steel, and the end is hardened and 
tempered to prevent it from twisting or rolling 
the edge when in use. It should never be used 
as a pry for separating parts as it may break 
the hardened end. 

If the screw driver breaks, the end may be 
restored by first forging it roughly to the 
proper shape and then grinding it on an emery 
wheel to the desired form and size. First heat 
the broken end, keeping it at a bright cherry 
red while forging, to prevent it from cracking, 
and using care not to overheat it as that would 
prevent proper hardening when finished. After 
forging, dress the end to the desired size on the 
emery wheel, then harden and temper. 

Tempering 

To temper the end of the screw driver, first 
heat it to a cherry red, then dip it 1/4" deep in¬ 
to clean water, holding it there until the red 
just leaves the steel. Remove it and polish it 
with emery cloth. The heat that remains will 
soften the tip just enough to temper it proper¬ 
ly. As the heat works down into the end, the 
color will change from a pale straw to a 
dark blue. When it has a light blue color, 
quench it in the water to prevent it from be¬ 
coming any softer. If the whole tip is cooled 
suddenly it becomes glass hard and brittle. 

The slot in the screw has straight sides, so 
■the tip of the screw driver should be ground 
accordingly, to prevent it from upsetting the 
edges of the screw slot. 

If there is only a small break on the end of 
the screw driver, it may be ground to restore 
the proper shape. Care should be used in the 
grinding to keep the end cool, because if it 
heats up until the end becomes a dark blue, 
the tempering will be spoiled and it will be 
necessary to harden and temper it again. 

TWIST DRILLS 

The twist drill is a tool used to cut round 
holes. Spiral grooves are cut in the sides of 
the drill, to allow the cuttings to pass out and 
also allow the lubricating oil to reach the cut¬ 
ting edges, when used. It is made of tungsten 
steel or high carbon steel, hardened, tempered 
and ground. The repair man is never required 
to harden a drill. 


Drills are made in various sizes, the stand¬ 
ard drills being in steps of 1/64". Drills be¬ 
tween the standard sizes are designated by 
numbers or letters. 

When grinding drills never hold them to the 
emery wheel long enough to heat them, as this 
softens the steel. 

In order to have a drill cut true to size, it is 
necessary to have the angles and the lengths 
of both of the cutting lips the same, with just 
enough clearance so that the cutting edge is 
the only part which touches the metal. Too 
much clearance will allow the cutting edge to 
brush off and become dull. If one lip is longer 
than the other, or at a different angle, the point 
of the drill will not be in the center, conse¬ 
quently, the drill will cut oversize. 

When drilling brass, the cutting lip of the 
drill should be ground flat, so that the cutting 
edge scrapes off the metal instead of shearing 
it. If the edge is not flattened, the drill will 
either break, or spoil the work when breaking 
through the under side of the metal. 

Do not run the drill too fast, or do not use 
one which is dull, as the friction heats and 
draws the temper from the drill. 

Always fasten the work rigidly to the drill 
press table, or if using the electric drill, hold 
the work rigidly. 

When drilling steel, use lard oil or soda water 
(or old engine oil). For aluminum drilling, 
use kerosene. Brass and cast iron should be 
drilled dry. 

REAMERS 

A reamer is a grooved cutting tool used for 
finishing to accurate size and smooth surface 
round holes that have already been drilled or 
bored to approximate size. It is made with 
numerous cutting edges around the outside, of 
the body, the edges being carefully ground to 
give the correct size. It is made of high grade 
carbon steel, hardened and tempered before 
the cutting edges are ground. The repair man 
should never attempt to harden or temper a 
reamer. 

The reamers used in the repair shop are the 
solid hand reamer and the hand expansion 
reamer. 

The solid hand reamer is not adjustable, but 
can be obtained in various sizes in steps of 
1/64". 


116 


TOOLS 


The expansion reamer is slotted and has a 
screw and conical plug in one end so arranged 
that turning the screw inward will increase the 
diameter of the reamer to a size slightly larger 
than standard. On account of the reamer be¬ 
ing quite hard, which is necessary to hold the 
cutting edges, the amount of expansion obtain¬ 
able is very limited, the maximum being about 
1/64". 

A reamer should always be turned in a clock¬ 
wise direction only, either when reaming or 
removing. When turned in this direction, the 
cutting edge is relieved slightly, to prevent rub¬ 
bing, and also has a backing of metal which 
prevents the cutting edge from being brushed 
off, broken or injured. If turned in the wrong 
direction, the reamer soon becomes dull. 

When reaming steel use a cutting oil, such 
as lard oil, as a lubricant. Cast iron and brass 
should be reamed dry. 

To insure a good accurately finished hole, 
leave only a very small amount of metal to be 
removed by the reamer. A reamer will chatter 
and cut oversize if too much metal is removed 
at one operation. Use a double end reamer 
wrench and be careful to keep the reamer true 
with the hole, as a slight tilting will cause the 
hole to be out of line and out of shape. 


CHISELS AND DRIFTS 

Chisels and drifts are forged of high carbon 
steel. 

Forge the end to the desired shape while 
cherry red, then grind it to the desired form 
and sharpen it on the emery wheel. 

Proceed with the hardening and tempering. 
When tempering, quench the chisel in the 
water when the color is just changing from a 
dark purple to a blue. 

As a result of the variation of the percentage 
of carbon in the steel, there is a variation in 
the degree of hardness obtained. 

The above tempering rule is correct for the 
best grades of tool steel. 

HAMMERS 

There are various kinds of hammers used 
in repair shop work. The hard steel ham¬ 
mer is used to drive, chisels, punches, etc., 
for riveting and ordinary uses, but for driving 
on finished surfaces, a hammer made of soft 
material should be used, such as a wooden mal¬ 
let, a lead, rawhide or rubber hammer. Never 
strike a finished surface or parts made of soft 
materials with steel or hardened hammers; use 
any of the soft hammers or a block of wood. 
Monkey wrenches and other tools are not to be 
used as hammers. 



^ 

=iF== 






F 


Hi 7 


2 



( 1 ) 

( 2 ) 


( 3 ) 

( 4 ) 


FIG. 87 

Twist drill. 

Hand expansion reamer. 

A. Adjusting screw. 

B. Slot. 

C. Relieved cutting edge. 

D. Cutting edge. 

Special screw driver. 

Chisel. 


4 
































TOOLS 


117 



FIG. 88 

BOLTS, SCREWS, NUTS AND STUDS 


A. Hardened cup-point set screw. 

B. Stud. 

C. Headless set screw, hardened. 

D. V-point set screw, hardened. 

E. Cap screw. 

F. Fillister head screw. 


G. Flat head screw. 

H. Round head screw. 

I. Castle nut. 

J. Plain nut. 

K. U. S. Std. thread. 

L. S. A. E. thread. 


Screws with U. S. Standard thread are commonly used in soft material, such as cast iron, brass. 

bronze, or aluminum. 


S. A. E. U. S. Std. 


Diam. 

Thds. per inch. 

Diam. 

Thds. per inch. 

y* 

28 


20 

A 

24 

■ft 

18 

% 

24 

% 

16 


20 

ft 

14 

Vz 

20 

Vz 

13-12 

■ft 

18 

ft 

12 

% 

18 

% 

11 

u 

16 

u 

11 

% 

16 

% 

10 

Va 

14 

Va 

9 

1 

14 

1 

8 


U. S. 60° V threads are used on both these standards. 
The top and bottom of the thread have a narrow flat 
surface, which is % of the pitch. 

The threads on the bolts may be re-cut with an adjust¬ 
able die, and the threads in the nut with the solid tap. 
These taps and dies may be obtained in either of the 
two standards, or for “number” bolts. Special taps and 
dies are made for odd size bolts and nuts. The tap not 
being adjustable, is of a standard size. Before fitting a 
nut to a bolt that is tight, run the tap through the nut; 
then, if it is necessary, run the die over the screw to 
obtain the proper fit. 

































































































































































118 


TOOLS 



FIG. 89 


MICROMETER 


The micrometer is an instrument used to’ 
measure in the thousandth part of an inch, and 
in some instances in one ten thousandth part 
of an inch. This instrument is made for 
measuring the thickness and diameter of fin¬ 
ished parts, the inside diameter of holes, and 
other measurements that are required to be 
extremely accurate. 

Micrometer adjustments are also incorpor¬ 
ated in various tools. It is a delicate instru¬ 
ment, should not be dropped or used roughly, 
but handled very carefully and kept free from 
dirt. 

Construction and Operation of the Micrometer 

The thimble (F) and the spindle (D) are 
one piece, with a screw of 40 threads per inch 
cut on the spindle. The spindle screws into 
the sleeve (E), which has a split taper nut in 
the upper end to take the end play out of the 
thread. The sleeve (E) is threaded at the 
lower end into the frame (A). By screwing 
this sleeve in or out the micrometer is read¬ 
justed in case of wear, or in case it should be 
dropped. A small spanner wrench is provided 
for this purpose, the wrench fitting into a 
small hole in the lower end of the sleeve. 

Outside micrometers generally have a range 


of one inch, as from 0 to 1", 1" to 2", 2" to 
3", etc., for which the sleeve is graduated. As 
the spindle has a 40 pitch thread, it requires 40 
turns of the spindle and thimble assembly to 
move it one inch. For each full turn the 
thimble moves up or down 1/40" or 25/1000" 
(.025"). 

The sleeve is graduated in tenths as indi¬ 
cated by the figures and the distance between 
any two of the numbered marks represents a 
tenth of an inch, or 100/1000" (.100"). The 
tenths are divided into four parts, each part 
being 1/40" or 25/1000" (.025"). The circum¬ 
ference of the lower end of the thimble is 
graduated into 25 parts, since for each full 
turn, it moves up or down 25/1000" (.025"). 

Reading the Micrometer 

To read the micrometer, it is necessary to 
observe the zero line (G) on the sleeve, the 
lower edge of the thimble and the mark on 
the thimble that comes in line with the zero 
line on the sleeve. 

Example: If the lower edge of the thimble 
is on the third line above 2 and the 0 mark on 
the thimble is in line with the zero line on the 
sleeve the reading will be .275". When the 0 
mark on the thimble is in line with the zero 

















































































TOOLS 


119 


line on the sleeve, the lower edge of the 
! thimble is just on one of the small cross-lines. 

! In the above setting (X) the lower ledge of the 
thimble is on the second line above the 2; 
therefore the reading is .250". 

Example: If the lower edge of the thimble 
was in line with 8, and the 0 on the thimble in 
line with the zero line on the sleeve, the read¬ 
ing would be .800". 

Example: Referring to the larger illustra¬ 
tion in Fig. 89, the reading is .178" -j- because 
the third mark from the zero on the thimble 
has just passed the zero line on the sleeve. 

Example: Consider that the lower edge of 
the thimble is between the second and third 
marks above 5, and the 18 mark on the thimble 
is in line with the zero line on the sleeve, the 
reading would be .568". 

Vernier or One Ten Thousandth Reading 

(. 0001 ") 

The “vernier" graduations are an addition 
to the regular micrometer, making it possible 
to measure to one ten-thousandth part of an 
inch. 

On the sleeve at one side of the zero line 
are eleven long lines, the space between these 
lines being just 9/10 of the space between the 
marks on the thimble. When any mark on the 
thimble is in line with the zero line (G) on the 
sleeve the two 0 lines on the vernier will be in 
line with two marks on the thimble. The 
other vernier marks will not be in line. If the 
mark on the thimble is not in line with the 
zero line on the sleeve, only one line of the 
vernier will be in line with one of the marks 
on the thimble. 

Reading the Vernier Micrometer 

The reading for the thousandths of an inch 
is the same as previously described; then note 
which line on the vernier lines up with the one 
of the marks on the thimble. 


Example: In illustration (Y), number 7 line 
on the vernier lines up with a mark on the 
thimble; the other lines are off; the reading is 
.2507", or two thousand five hundred and seven 
ten thousandths of an inch. 

When measuring, place the micrometer over 
the work and screw down on the thimble until 
the spindle just touches the work. Do not 
force the thimble. Then read the setting. 

Some micrometers are constructed with a 
small knurled handle on the outer end of the 
thimble, which is used for two purposes. It 
is attached with a ratchet connection, so that 
the action is positive in one direction, but 
when tuning it in the other direction and the 
spindle comes to rest on the piece that is being 
measured, or on the anvil (B), the ratchet will 
allow the knurled handle to continue turning. 
This prevents the operator from turning the 
spindle too tight against the work, and insures 
a unifonii pressure of the spindle in all read¬ 
ings. The handle is smaller in diameter than 
the thimble, so that in moving the spindle 
through longer distances, it can be turned 
much faster by using the handle. 

Testing the Micrometer for Accuracy 

Place a piece of paper on the anvil, screw the 
thimble down until the spindle pinches the 
paper, then draw the paper away; this is done 
to remove dirt and to insure the spindle resting 
on the anvil; then turn the thimble until the 
spindle just touches the anvil, or if the ratchet 
is used, screw the thimble down with the 
ratchet until the ratchet slips, which will be 
when the spindle touches. The reading should 
then be 0, or the 0 on the thimble should be in 
line with the zero line on the sleeve. If the 
zero line is either side of the 0 mark on the 
thimble, use the spanner wrench to turn the 
sleeve until those lines do line up, when the 
spindle is just touching the anvil. 





120 


TOOLS 



FIG. 90 
WRENCHES 


A. Pipe wrench (Stillson). 

B. Monkey wrench. 

C. Adjustable end wrench. 

D. Open end wrench. 

These tools are generally made of a high grade steel 
having hardened jaws to prevent the edges turning over 
and to prevent the jaws from bending. Wrenches are 
designed in various shapes, some being adjustable. 

Illustration (A) shows an adjustable pipe wrench, also 
called a Stillson wrench. This wrench is used to 
turn pipes or round pieces, but should never be used on 
finished or hardened surfaces, as it will mar the sur¬ 
face or dull the wrench. These wrenches may be ob¬ 
tained in various lengths. 

Illustration (B) is a Monkey wrench, and is adjust¬ 
able; the jaws are hardened. 

Illustration (C)’ shows an adjustable end wrench. This 
wrench is more universal than the monkey wrench, be¬ 
cause the opening is at an angle and the jaws are not as 
heavy. 

Illustration (D) represents an open end wrench. 
These wrenches may be obtained to fit the various size 
bolts and nuts. The wrenches are numbered, the num¬ 
bers being standard as to sizes. 

The arrows indicate the direction the wrenches should 
be moved when placed as shown. If it is required to 


turn the nuts or pipe in the other direction, the wrench 
should be reversed. 

A good rule to remember is to move the wrench in the 
direction that will press the adjustable jaw inward. 


FLAT WRENCHES 


Wrench 

Number 

Size 

Open¬ 

ing 

Wrench 

Number 

Size 

Open¬ 

ing 

S.A.E. 

Bolts 

Nuts 

Diam. 
of head 
across 
Flat 

Wrench 

Number 


Inches 


Inches 




21 

A-H 

126 

A-A 


tV ' 

126 

22 


127 

H-A 

A' 

Vi’ 

22-23-25 

23 

H-H 

128 

y-ys 



26-127-128 

24 

H-H 

129 

■h-% 

%’ 

A' 

126-127-129-130 

25 

y2-H 

130 

A-M 

A' 

Vs' 

128-129-131-132 

26 

y-H 

131 



H' 

130-131-133-134 

27 

H-n 

132 

Vs- a 

A' 

Vs' 

30-31-33-34 

28 

B-B 

133 

H-H 



134-135-137-138 

29 

B-B 

134 

H-Vs 

Vs’ 

B' 

32-33-35-36 

30 

H-H 

135 

H-Vs 

B' 

1' 

136-137-139-140 

31 

H-H 

136 

B-l 

y*’ 

lA' 

34-35-37 

32 

B-B 

137 

Vs-l 

Vs' 

IK' 

36-37-140 

33 

Vs-H 

138 

Vr-W 




34 

^-lA 

139 

1-1M 




35 

B-IA 

140 

1-lK 




36 

H-iy 






37 

lA-iJi 

























CHASSIS 


The chassis includes all the parts of an auto¬ 
mobile except the body and its attachments. It 
consists of the frame, springs, power plant, 
clutch, transmission system, axles, wheels, 
steering gear and the control apparatus. 

The frame is made of pressed or rolled steel 
or laminated wood. The steel frame is most 
commonly used because of its strength and 
because it can be manufactured speedily. The 
main side frames are riveted and welded to¬ 
gether through cross members which serve to 
brace it and also support the power plant and 
transmission system. The wood frame, al¬ 
though little used, is lighter in weight, more 
flexible and assists in absorbing the shocks 
encountered in driving. It is expensive to 
manufacture and difficulty is experienced in 
obtaining good grade of stock for it. 

The springs are interposed between the 
frame and the axles and act as cushions to 
take the jars and bumps due to unevenness of 
the road. They protect the engine and other 
delicate parts against undue shock and vibra¬ 
tion and insure easy riding. 

The power plant consists of the engine and 
all its auxiliaries and includes fuel system, car¬ 
buretor, ignition apparatus, lubricating and 
cooling systems, starting and lighting appar¬ 
atus. It may be mounted upon the side frame 
and cross members or set in a sub-frame in 
either of two ways, three-point or four-point 
suspension. 

In the three-point suspension, the front of 
the engine rests upon the center of the front 
cross member of the frame while at the rear of 
the engine there are two projecting arms which 
rest upon the side members of the frame. In 
the four-point suspension, there are four pro¬ 
jecting arms on the engine which rest upon the 
side frames. 

The power plant, clutch and transmission are 
frequently combined, forming what is called 
a “unit power plant.” If the transmission is 
separate, it is mounted upon cross members of 
the frame, either “amidship” or on the rear 
axle. 

The axles carry the weight of the car as 
transmitted to them through the springs. The 
rear axle construction is special on account of 
its serving two purposes, carrying the weight 
and also propelling the car. The front axle is 
solid and the front wheels mounted on pivoted 
spindles to permit steering the car. 

Wheels are of three kinds, wood, wire and 
disc steel, all being equipped with some form 
of rubber tire, usually pneumatic type, consist¬ 


ing of strong outside casing with air inflated 
inner tube, to assist in protecting the car from 
shock and vibration and insure easier riding. 
The rear wheels are equipped with brakes, 
usually two, for slowing down and stopping the 
car. The two brakes are termed “foot brake” 
and “hand brake.” The foot brake is for gen¬ 
eral use, and the hand brake for use in case the 
foot brake fails. It is provided with means for 
holding the brake when applied, to prevent the 
car from moving if left standing. 

The steering mechanism is mounted upon 
the side frame and projects up into the driver’s 
compartment. It provides means for steering 
the car and has levers mounted upon it for 
controlling the throttle valve and the spark 
advance and retard on the ignition apparatus. 

BEARINGS 

The bearings employed in the construction 
of front wheels, steering devices, clutches, 
transmissions, differentials, and rear axles 
may be either plain bronze, babbitt, plain 
roller, tapered roller, cup and cone, single or 
double row annular, ball thrust, or plain thrust 
bearings. The bronze and babbitt bearings 
may be either the divided or the bushing type. 

The bushing type bearing is pressed into the 
housing, while the divided type has a bearing 
cap which permits adjustment to compensate 
for wear. The divided type is necessary in 
many cases in order to remove the parts, as, 
for instance, the connecting rod and main bear¬ 
ings of the engine. After bronze or babbitt 
bearings are fitted into place they should be 
reamed or scraped to the proper size. The 
bronze or babbitt bearings, if well lubricated, 
develop less friction than the average plain 
bearings, but the friction in these bearings is 
considerably higher than that developed by the 
roller or ball bearings. 

Roller or ball bearings operate on hardened 
surfaces, and are polished to as high a finish 
as is mechanically possible. 

The materials used in these bearings are al¬ 
loy steels, heat treated and hardened to reduce 
wear, also to make them tough but not brittle. 
The machining and finishing of these bearings 
determines the length of service to a great ex¬ 
tent. The smoother the surfaces the less the 
friction, consequently the less wear. Bearings 
of this type require less lubricant, as the fric¬ 
tion and heat developed is very low. The heat 
developed by friction breaks up and evaporates 
the oil on the bearings. 




122 


CHASSIS 


Plain Roller Bearing 

This bearing is designed for radial load only, 
taking no end thrust. The plain roller bearing 
is constructed of an assembly of rollers that 
roll between two hardened steel sleeves. The 
roller bearing is constructed either with an 
inner and outer race assembled with the 
rollers, or else they roll on the inside of a 
hardened steel race and on the outside of a 
hardened shaft. If the material in the shaft is 
such that it can be heat treated and hardened, 
it is not necessary to provide an inner race for 
the rollers. The surface with which the rollers 
come in contact must be hardened and ground 
to as high a finish as possible. In case of wear, 
these bearings are adjustable to a very small 
extent. 

A shim of thin sheet copper or brass may 
be placed around the outside of the outer 
race, the race being split to allow it to con¬ 
tract. This will take up some of the clear¬ 
ance, but if it is too great it is best to provide 
a new outer race. Where end thrust comes 
on a shaft that is mounted on a plain roller 
bearing a special end thrust bearing is pro¬ 
vided, as this plain roller bearing takes no 
end thrust. These bearings may be lubricated 
either by oil or grease, depending entirely 
on where they are installed. 

Tapered Roller Bearing 

Tapered roller bearings take both radial and 
end thrust loads and are adjustable to compen¬ 
sate for wear. Should a bearing of this type 
wear on any of its bearing surfaces, it is so 
arranged that the play can be removed by 
bringing the races closer. The tapered roller 
bearing is constructed of three principal parts; 
an outer and an inner race, and a row of tap¬ 
ered rollers. 

These parts are made of a high grade alloy 
steel, heat treated, hardened and ground to a 
very high finish. The rollers are held in a re¬ 
tainer, which prevents them from coming in 
contact with one another. The outer and inner 
race should be a light tapping fit in the hous¬ 
ing and on the shaft. When ordering new parts 
for bearings of this type, always order by the 
number which is stamped upon either the outer 
or inner race. 

Cup and Cone Bearing 

The cup and cone bearings take both radial 
load and end thrust and are adjustable. The 
bearing is constructed of three principal parts: 
the outer cup, the inner cone, and a row of 
balls which roll between cup and cone. 

The cup, cone and balls are made of high 
grade alloy steel, heat treated and hardened. 


then ground for accuracy and finish. The 
outer cup is pressed lightly into the housing, 
while the inner cone should be a light tapping 
fit on the shaft. They should never be driven on 
so tightly that the pressure will spring the 
races. When a load comes onto a sprung 
bearing it is taken on a few spots only, con¬ 
sequently it will wear very fast. 

There is an adjusting nut provided to set 
the cup and cone closer together. Either the 
nut will be resting against the outer cup or 
against the inner cone, so that as the nut is 
turned in, it will bring the cone closer to the 
cup with the row of balls between. This 
adjustment is to take up whatever play there 
may be. This type of bearing is used consid¬ 
erably on front wheel spindles although other 
bearings may be used. 

Adjustment of Cup and Cone 

There should be only enough clearance be¬ 
tween the balls and the races to prevent them 
from binding. To adjust this bearing, turn 
the adjusting nut until the bearing is tight, or 
until there is no play in the bearng. Then back 
the nut away sufficiently to relieve all tight 
spots, but not enough to allow any play. If 
there is too much play in these bearings, the 
balls will have a chance to pound the races 
out of round. With the race out of round, the 
balls will be fiattened, consequently the bear¬ 
ing will be scored or roughened. 

When replacing new parts for a cup and 
cone bearing, either the outer cup or cone may 
be replaced separately, but if the balls are 
worn replace the entire set. A heavy load, if 
taken on one or two balls only, causes the 
races and balls to wear rapidly. 

When disassembling a bearing of any type, 
care must be taken that neither the race nor 
the balls become rusted, because the rusting of 
these surfaces roughens them so that the 
finish will be marred. To prevent this, when 
removing the bearings, always cover them 
with grease or heavy oil, which prevents the air 
and moisture from coming in contact with the 
finished surfaces. Also, when bearings are 
being assembled, be careful not to allow any 
filings or particles of dirt of any description 
to come onto the surface of the bearing. The 
smallest particle of dust may cause the surface 
of the bearings to become roughened. The life 
of the bearings depends upon the finish. The 
better the finish and the material used in their 
construction, the longer they will wear. 

Single Row Annular Beauring 

Single row annular type bearings are de¬ 
signed to take radial load only, although the 
bearing will take about one-third as much end 




BEARINGS 


123 



CUP AND CONE 


ANNULAR BALL BEARING 
SINGLE ROW DOUBLE ROW (RIGID) 


FIG. 91 


BEARINGS 


This figure shows some of the different types of bear¬ 
ings employed in the chassis. In the Tapered Roller 
bearing the outer race is moved by the adjusting nut. 
This removes the play between the rollers and the 
races. Another common mounting is to press the outer 
race into the housing and against a shoulder with an 
adjusting nut mounted on the shaft against the inner 
race. 

The Ball Thrust bearing mounted with the Plain 
Roller bearing is adjustable either by an adjusting nut 
as shown or by placing thin metallic shims between the 
race and the shoulder of the mounting. The Plain 
Thrust bearing with a babbitt or bronze washer between 
two hardened steel races is mounted in the same man¬ 
ner, except that the races are pinned to the mounting 
and no adjusting nut is used. The adjustment is made 
either by placing thin metallic shims back of the 


races or by replacing the main thrust washer with a 
thicker one. 

The Flanged Roller bearing may be adjusted for end 
play by tightening the adjusting nut mounted inside 
the housing against the outer race. The adjusting nut 
may be mounted on the shaft against the inner race. 
This bearing is not adjustable for radial wear. 

The Cup and Cone bearing is adjusted by tightening 
the adjusting nut against the cone. The adjusting nut 
may be mounted inside the housing against outer race. 

The Single and Double Row Annular bearings are not 
adjustable, but the mounting can be adjusted as shown, 
by an adjusting nut either on the shaft or in the 
housing. Where no adjusting nut is provided the 
bearing may be adjusted by placing thin metallic shims 
between the race and mounting. 




















































































































































124 


C H A S S I S 


thrust as radial load. This is not sufficient 
for the usual requirements. An extra ball 
thrust bearing may be provided, or a double 
row annular bearing may be used, depending 
entirely upon where the bearing is mounted. 
Sometimes only a single row annular bearing 
is used where there is an end thrust, but it 
causes the bearings to wear excessively. Bear¬ 
ings of this type are not adjustable to compen¬ 
sate for wear. 

The single row annular bearing consists of 
an outer and inner race and a row of balls held 
by a retainer. The outer and inner races have 
grooves cut in them and are ground with 
a larger radius than that of the ball and is 
expected to take load in radial direction only, 
so with this construction it is evident that the 
end thrust throws the bearing out of the true 
alignment upon which it is designed, causing 
uneven wear. 

When these bearings wear it is necessary to 
install a complete bearing. They are assem¬ 
bled at the factory and, because of their 
construction, it is not advisable for the 
mechanic to repair them. The number or size 
of the bearing is stamped on the side of the 
outer or inner race. These bearings are usually 
measured by the metric system. A bearing 
may be ordered from any maker, by the num¬ 
ber, and the bearing will fit. 

These bearings are made in light, medium 
and heavy series. The inside diameter of the 
inner race is the same on all the series, but in 
the larger series, the outer diameter, width of 
the bearing and the diameter of the balls in¬ 
creases. So if the bearing is ordered by the 
number, the right size will be obtained. Both 
the outer and inner race should be only a light 
tapping fit in the housing and on the shaft. If 
driven on tightly, it will spring races, causing 
binding and wear. 

Double Row Annular Bearing 

Double row annular bearings are constructed 
in two types; the rigid and the flexible bear¬ 
ing. The flexible double row annular bearing 
is not used in automobile construction, but is 
employed usually on line shafts where there 
is a tendency for the shaft to become out of 
alignment. The bearings of this type allow 
greater flexibility. The double row annular 
bearing when used on the automobile, takes 
both the end thrust and radial loads. The 
shoulders extending farther over the sides of 
the balls make it possible for this bearing to 
take a greater end thrust than the single row 
type. This bearing is not adjustable. 

Should the bearing become worn it is neces¬ 
sary to replace it with a complete bearing. 


The bearing should be kept clean and properly 
lubricated. When ordering new bearings give 
the series number and the type. 

Bearings may be mounted on shafts where 
there is considerable end thrust due to the sep¬ 
arating effect of bevel gears or in the wheels 
where there are thrust strains caused by skid¬ 
ding. An end thrust bearing must be provided 
to take this thrust. The cup and cone bearing 
and the tapered roller bearing take both radial 
load and end thrust, but where the plain roller 
or singular row annular ball bearing is used 
and the end thrust is very great it is necessary 
to provide a separate thrust bearing. 

The thrust bearings used are either the ball 
or plain thrust type. 

Ball Thrust Bearing 

The ball thrust bearing consists of a row of 
hardened steel balls revolving between the sur¬ 
face of two flat hardened steel discs. An end 
thrust bearing takes no radial load. The steel 
discs may have either a groove on the surface 
for the balls to revolve in, or else the balls roll 
between the fiat surfaces and are held in place 
by a retaining ring. 

Bearings of this type are made with holes to 
fit the various sized shafts. They may also 
have larger outer diameters and balls. The 
larger the balls the greater the thrust that can 
be taken on the bearing without excessive 
wear. 

Thrust Plates or Plain Thrust Bearings 

Plain thrust instead of ball thrust bearings 
are provided in some instances to take the 
end thrust. The plain thrust bearing consists 
of two hardened steel plates with a babbitt, 
bronze, or cast iron plate or spacer between 
them. The softer metal washer mounted be¬ 
tween the hardened steel plates reduces the 
friction, but not as much as the ball bearing. 
The thrust plates resist wear very well if they 
are well lubricated. Plain thrust plates take 
end thrust only. The plain thrust bearing is 
adjustable only by replacing the worn parts or 
by adding or removing thin metallic spacing 
shims. 

FRONT AXLES 

Types ^ 

Front axles are made in either the tubular) 
or the I-beam section type. The I-beam section 
is the type more commonly used on automo¬ 
biles. 

Front axles are made of high grade alloy 
steel, heat treated to increase their strength. 




BEARINGS—FRONT AXLES 


125 


Mounting 

The front axle is fastened to the frame 
through the springs and their mountings. This 
construction differs from the front axle of a 
wagon in that the steering knuckles only are 
pivoted instead of the entire axle. Front axles 
have the spring seats or the surfaces upon 
which the springs are mounted, machined and 
drilled. The drilled holes are for the spring 
clips and the centering pin on the spring. 

The outer end of the axle is made either 
solid or forked to accommodate the steering 
knuckle. In the ends of the axle are drilled the 
holes for the pivot bolt or pin. 

Alignment 

The pivot bolt holes may be employed 
to check the alignment of the axle should it 
become sprung. The alignment may also be 
checked from the spring seats if they are ma¬ 
chined. The two pivot bolt holes are usually 
parallel and at right angles to the face of 
spring seat. 

When straightening front axles and align¬ 
ing them by the two pivot bolt holes, use 
two straight rods three or four feet long of the 
same diameter as the pivot bolt, placing them 
in the holes and then measuring the distance 
between the rods at the top and bottom. They 
should be parallel. 

It is not advisable to heat an axle red hot 
while straightening, as the high temperature 
will remove the strength obtained by the heat 
treatment. There is no danger of breaking an 
axle while attempting to straighten it cold, but 
it usually requires a high pressure straighten¬ 
ing press to accomplish this. When the lack of 
equipment makes it necessary to heat the axle 
to straighten it, it is not advisable to have 
the temperature any higher than is absolutely 
necessary. 

Caster Elffect 

When the axle is properly mounted, the 
pivot bolts and axle are inclined forward 
toward the bottom usually about 5°. This is 
termed caster effect, and is obtained either by 
the machining of the spring seat, the manner 
in which the spring is mounted, or by driving 
a wedge between the spring and its seat. 

This caster effect is based on the same 
principle as is used in the front fork of a 
bicycle, which is bent forward, to take the 
strain of the road shocks behind the spindle 
instead of directly in line. This gives a spring 
effect, which reduces vibration and makes 
steering easier, 

STEERING KNUCKLE 

The steering knuckle is usually a drop forg¬ 
ing, formed under big drop hammers. It is 


made of high grade alloy steel, properly heat 
treated. The steering knuckles are mounted 
in or on the end of the front axle, and should 
fit snugly. The steering knuckle is drilled to 
accommodate the pivot bolt, which in most 
cases is secured rigidly in the axle. If there is 
too much play between the steering knuckle 
and the axle, it causes a knock which is very 
noticeable when driving over rough pavements. 

Fitting 

Bushings or bearings are pressed into the 
steering knuckles and reamed to a snug fit, 
so that it is just possible to push the pivot 
bolt through with the palm of the hand without 
binding. The bushings or bearings sometimes 
have shoulders or flanges which rest against 
the outside of the steering knuckle. The shoul¬ 
ders or flanges take the thrust due to steering 
and carry the weight of the car. In some 
cases, as on heavy cars or trucks, instead of 
having the bronze shoulders, ball thrust bear¬ 
ings are employed. This reduces friction and 
makes steering easier. 

When the bearings wear, new ones may be 
pressed in and a reamer run through the two 
bushings so as to properly align their holes. 

Should the steering knuckle become sprung, 
it is difficult to straighten it properly, due to 
the short leverage and to the various angles 
which are unknown to the repair man. It is 
advisable to replace with a new steering 
knuckle. 

PIVOT BOLTS OR PINS 

The pivot bolt or pin is made of high grade 
alloy steel, heat treated, hardened and ground 
to reduce wear. It is hollow, at least to the 
depth of the bearings, with a hole at right 
angles leading to the bearings for lubricating 
them. 

A grease cup is usually provided in the upper 
end of the pivot bolt. Proper lubrication 
makes steering easier, causes the steering 
mechanism to be more quiet in operation, and 
also gives longer life to the pivot bolts and 
their bearings. 

CAMBER 

On the steering knuckle is a spindle, upon 
which the front wheel is mounted. The spindle 
is set at an angle of from 1° to 5° from a line 
parallel with the axle (see rear view of axle. 
Fig. 92, page 126). This causes the front 
wheels to “set-in,” or to be closer together at 
the bottom, which reduces the distance be¬ 
tween the center line of the pivot bolt and the 
center line of the wheels at the point of con¬ 
tact with the road. 

The steering knuckle turns around the 
pivot bolt when steering. The point of the 
wheel that is in contact with the road is not 




126 


CHAS SIS 



FRONT AXLE 














































































































































































STEERING KNUCKLES 


127 


directly underneath the center of the pivot 
bolt. Consequently, the wheel must neces¬ 
sarily travel in a circle around the center line 
of the pivot bolt when steering. When de¬ 
scribing this circle, the wheel is dragged over 
the road, making steering difficult and causing 
wear of the tires. If the wheels were set at an 
angle great enough to bring the point of road 
contact directly underneath the center line of 
the pivot bolt, the strain of steering would be 
greatly reduced. This is not practical, as an 
excessive strain would come on the wheels and 
bearings. The angle the spindle is set is gov¬ 
erned by the width of the bearings and the 
diameter of the wheel. This angle is termed 
“camber.” It is not adjustable. 

STEERING KNUCKLE ARM 

The steering knuckle arm is the arm to 


which the tie rod is fastened. This rod con¬ 
nects the two steering knuckle arms and is 
adjustable. 

When the tie rod is mounted behind the 
axle, as it is in most cases, for protection, the 
two knuckle arms are set at an angle greater 
than 90° from the center line of the spindle. 
The reason for this construction is that when 
turning a corner, the inner wheel must swing 
through a greater angle than the outer wheel, 
due to the manner in which the axle is 
mounted. On a wagon, when turning a cor¬ 
ner, the axle swings, thus moving the inside 
wheel backward and the outside wheel for¬ 
ward. This differs on a car, due to the axle 
being stationary and the spindles being pivoted 
to its ends, which necessitates swinging one 
wheel through a greater angle than the other. 
It is accomplished by placing the steering 



FIG. 93 


STEERING KNUCKLE AND FRONT WHEEL 
MOUNTING 


A. 

Steering knuckle spindle. 

F. 

Grease cup. 

K. 

Steering knuckle arm. 

B. 

Front wheel hub. 

G. 

Oil hole. 

M. 

Front axle. 

C. 

Hub cap. 

H. 

Steering knuckle bushing. 

N. 

Spring seat. 

D. 

Spindle washer. 

I. 

Steering knuckle. 

0. 

Spoke. 

E. 

Spindle nut. 

J. 

Steering knuckle thrust arm. 

P. 

Felt washer. 


In this construction the pivot pin is pressed into the 
axle snugly and locked with a set screw to prevent a 
movement of the pin in the axle. The steering knuckle 
has its bearings on the stationary pin. The bronze 
bearing bushings pressed into the steering knuckle re¬ 


duce friction and the wearing of the pivot pin. 

To remove the pivot pin for replacement of these 
bushings, unscrew the upper and lower retainer caps 
and the pivot pin set screw, press the pin out and re¬ 
move steering knuckle. 























































































128 


CHASSIS 


knuckle arms at an angle greater than 90° 
from the spindle, causing one steering arm to 
swing away from the center line of the pivot 
bolt and the other to swing toward it. 

TOE-IN 

The front wheels are closer together at the 
front than they are at the rear, or are said to 
“toe-in.” This “toe-in” or “gather” of the front 


wheels is necessary to counteract the action 
which results from the wheels being cam¬ 
bered. When a car is in motion, the front 
wheels tend to roll outward, due to the 
camber, the same as a hoop when rolled along 
on the floor at an angle will have a tendency 
to roll in the direction it is leaning. This 
spreading effect will cause the tires and bear¬ 
ings to wear. To counteract this, the wheels 



STEERING KNUCKLE AND FRONT WHEEL 
MOUNTING 


A. Steering knuckle spindle. 

B. Steering knuckle. 

C. Front axle. 

D. Spindle nut. 

E. Spindle washer. 

F. Front wheel hub flange. 

G. Felt washer. 

In this construction the pivot bolt is threaded into 
the axle and locked by the castle nut on the lower end. 
A ball thrust bearing is mounted on the upper end of 
the steering knuckle to reduce the friction when 
the knuckle turns. Bronze bushing bearings are pro¬ 
vided for the pivot bolt. Lubrication is provided by 


H. Steering knuckle thrust bearing. 

I. Steering knuckle bushing. 

J. Oil groove. 

K. Steering knuckle thrust arm. 

L. Steering knuckle tie rod. 

M. Grease cup. 

N. Wheel bearings. 

the grease cup (M) through the channel (J). 

To remove the steering knuckles, remove the cotter 
pin and castle nut on the lower end of the pivot bolt, 
then unscrew the pivot bolt from the axle and drive it 
out the remainder of the way. 











































































STEERING KNUCKLES 


129 


are turned inward. The toe-in varies according 
to the amount of camber of the front wheels, 
but the wheels are generally from 14 " to %" 
closer together at the front than they are at 
the rear. 

The toe-in may be changed by either 
lengthening or shortening the tie rod, depend¬ 
ing upon where it is mounted. To line up the 
front wheels, raise them clear of the floor by 


the aid of a jack, then place them as nearly as 
possible in line with the rear wheels. Spin 
each wheel in turn, holding a piece of chalk 
against the tread, marking a line in the center 
of the tread all the way around. Measure the 
distance from one center line to the other 
center line in the front and in the rear of the 
wheels. The measurements should be taken 
halfway up on the tires or at the height of the 



A. 

Steering knuckle spindle. 

H. 

Steering knuckle bushing. 

B. 

Felt washer. 

I. 

Steering knuckle thrust arm. 

C. 

Front wheel hub. 

J. 

Wheel bearings. 

D. 

Hub cap. 

K. 

Steering knuckle tie-rod end. 

E. 

Spindle nut. 

L. 

Steering knuckle arm. 

F. 

Grease cup. 

M. 

Oil groove. 

G. 

Front axle. 

N. 

Steering knuckle. 


In this construction the pivot bolt is made secure in 
the axle, the steering knuckle having two flanged bronze 
bearings pressed into it to reduce the friction caused by 
the radial and end loads. These bronze bearings can 
be removed, if it should be necessary to replace them. 


The bearings are lubricated by the grease cup (F) 
through the channel (M). 

To remove the steering knuckle, remove the cotter 
pin and the castle nut at the lower end of the pivot 
bolt, then drive the pivot bolt from the axle. 

















































































































































































130 


CHASSIS 



FIG. 9G 


























































































STEERING KNUCKLES 


131 


FIG. 96 

STEERING KNUCKLE AND FRONT WHEEL 
MOUNTING 

A. 

B. 

C. 

D. 

E. 

F. 


Wire spokes. 

G. 

Thrust bearing. 

Steering knuckle spindle. 

H. 

Steering knuckle thrust arm. 

Wheel bearings. 

I. 

Front axle. 

Front wheel hub. 

J. 

Spring leaves. 

Oil hole. 

Steering knuckle bushing. 

K. 

Spring seat. 


In this construction the steering 
knuckle spindle and pivot bolt 
are all in one piece. Better lubri¬ 
cation is possible by the large 
oil hole (E), which acts as an oil 
reservoir. The oil flows through 
the spiral cut oil groove onto the 
bushing (F), then through the ver¬ 
tical groove to the lower bearing 
(G), which takes the load of the 
ear. The oil retaining cap at the 
bottom prevents loss of oil, making 


this bearing and mounting prac¬ 
tically oil tight and dust proof. 

To remove the steering knuckle 
assembly, remove the oil retaining 
cap, castle nut, bearing nut and 
bearing located below bearing (G), 
then lift the steering knuckle as¬ 
sembly out of the axle. If the bush¬ 
ing (F) is worn, it should be split 
and removed through the top. 
Press in a new bushing and ream 
to fit. 


End play of the pivot bolt in 
the axle may be eliminated by 
tightening the bearing retaining 
nut below the bearing (G). The 
wheel hub is a conventional mount¬ 
ing employing tapered roller bear¬ 
ings and an adjusting nut. The oil 
retaining cap is threaded inside the 
hub. The hub cap threaded on out¬ 
side of the hub holds the wheel 
flange on. This provides a “quick 
change” mounting for the wheel. 


wheel hub. The distance in front should be 
from 1/4" to less than in the rear. 

Automobile manufacturers give the correct 
measurement in their instruction books and it 
varies on different cars. The tie rod must be 
locked at each end to prevent it from working 
loose as a result of vibration. 

The tie rod is fastened to the steering arms 
of the steering knuckle by means of the tie rod 
end, which is fork shaped, fitting over the 
steering arm and held in place by the steering 
knuckle tie rod pin. This pin is hardened and 
ground, and is locked in place with a castle nut 
and cotter pin. It is lubricated either by means 
of an oil or grease cup. 

Some axles have the tie rod in front, with the 
steering arms set outward at an angle less 
than 90° from the center line of the spindle. 
The disadvantage of this mounting is that in 
case of a collision the tie rod is likely to be 
sprung and the toe-in changed, while if the 
rod is at the rear of the axle, it is well pro¬ 
tected. 

To increase the toe-in or gather of the front 
wheels when the tie rod is at the rear of the 
axle, lengthen the rod; if the tie rod is in front 
of the axle the rod must be shortened. 

One steering knuckle has the knuckle thrust 
arm connected to it, either by being forged 
integral with the steering knuckle or bolted 
on. The thrust arm is connected to the steer¬ 
ing device by means of the steering gear con¬ 
necting rod (sometimes called drag link). The 
steering knuckle thrust arm has a ball end, 
which seats in a socket in the connecting rod. 

The ball and socket joint is held together by 
a nut and a strong coil spring. The purpose 
of'this spring connection is to absorb the small 


shocks due to the roughness of the road and 
to prevent these shocks and vibrations from 
being transmitted to the steering device. The 
spring pressure in this connecting rod is ad¬ 
justable. 

The ends of the rod are packed with grease, 
usually held in by a leather boot, which is 
laced around the ball and socket joint. 

FRONT WHEEL MOUNTING 

The bearings employed in the front wheels 
are usually the cup and cone, or the tapered 
roller type. There are two bearings used in this 
mounting, one on each end of the spindle, 
and are mounted opposed, in such a manner 
that they take the thrust in both directions. 
These bearings are adjustable to compensate 
for wear. The inner race or cone of these 
bearings is a light tapping fit on the spindle, 
while the outer race should fit the same into 
the hub. 

To adjust the front wheel bearings, lift the 
wheels clear of the floor so that they are free 
to revolve. Remove the hub cap and cotter 
pin. Screw the adjusting nut inward until all 
play is removed. Turn the castle nut back 
until the first slot lines up with cotter 
pin hole. Replace cotter pin and test. If the 
bearings are free (not binding) and properly 
adjusted, the weight of the tire valve, when 
placed in a horizontal position, will cause it 
to settle to the bottom. If the valve does not 
settle to the bottom, turn the nut back to 
the next slot and test again. If the bear¬ 
ings are adjusted too tightly, it causes them to 
wear quickly. When mounting or adjusting 
these bearings, see that they are clean, that 
the adjusting nut is properly locked and that 
the bearing is well lubricated. 




132 


CHASSIS 


STEERING DEVICES 
Types 

The steering devices that are employed on 
present day cars are divided into two distinct 
classes, irreversible and reversible. Each class 
is subdivided into several types. 

The worm and wheel, the worm and sector, 
the split nut (or Jay-Cox) and the worm and 
nut are of the irreversible type. The reversible 
class has in its group the planetary and the 


ordinary gear reduction types. Cars equipped 
with irreversible type steering devices are 
easier to drive, due to the fact that the vibra¬ 
tion and skidding strains of the front wheels, 
when driving over rough roads or through 
ruts, are not transmitted back to the steering 
wheel, as is the case with the planetary and 
the plain gear reduction types. 

In designing steering devices, it is desirable 
to obtain as much leverage as possible, as this 
makes steering easier. The increased leverage 
is obtained by a gear reduction and the heavier 


STEERING KNUCKLE AND FRONT WHEEL 
MOUNTING 



A. Grease cup. 

B. Hub cap. 

C. Spindle nut. 

D. Pivot bolt bushing. 

E. Tie rod pin and nut. 

F. Tie rod adjustment lock. 

G. Pivot bolt. 

On this construction the hub cap is secured to the 
wheel flange instead of being threaded on to the wheel 
hub. This acts as an oil retainer and excludes the sand 
and grit. 

To remove worn pivot bolt bushings (D), remove 
the nut (H), press the bolt out, remove the steering 
knuckle and press out the bushings—then replace 
and fit new ones. 


H. Pivot bolt nut. 

I. Spindle washer. 

J. Cup and cone bearing. 

K. Hub cap fastening screw. 

L. Thrust arm ball end. 

M. Tie rod. 

To adjust the toe-in of the front wheels, remove nut 
(E), press out the tie rod pin, loosen the clamping bolt 
(P), and turn the tie rod end clockwise to decrease, or 
counter clockwise to increase the gather. With the tie 
rod pin removed, the bushing may be pressed out of 
the knuckle arm and a new one pressed in, using 
an expansion reamer to fit the pin—a light pressing fit 
with the palm of the hand. 






































































































STEERING DEVICES 


133 


the car, the greater the leverage required. In 
a steering gear of the reversible type,, the 
strains transmitted back through the steering 
device, due to vibration caused by road shocks, 
are greater than with the irreversible type. 


Worm and Wheel Steering Device 

(See Fig. 98) 

The worm and wheel steering device is con¬ 
structed as follows: A hardened steel worm is 



FIG. 98 

WORM AND WHEEL STEERING DEVICE 


A. 

Steering wheel shaft. 

H. 

Steering worm gear. 

B. 

Steering column tube. 

I. 

Eccentric bushing clamping hub. 

C. 

Grease filler plug. 

J. 

Steering arm shaft. 

D. 

Adjusting nut clamping lug. 

K. 

Steering gear arm. 

E. 

End play adjusting nut. 

L. 

Ball end. 

F. 

Thrust bearing. 

M. 

Clamping bolt. 

G. 

Worm. 

N. 

Radial bearing bushing. 


To remove the end play, loosen the clamping bolts in 
(D) and turn the adjusting nut (E) in, forcing the upper 
thrust bearing and worm against the lower bearing and 
housing. To remove the clearance between the teeth of 
the worm and worm wheel, loosen the clamping bolt (M) 
and turn the eccentric bushing around until the thicker 
part of the bushing is down and the worm wheel is 


forced upward. This play between the teeth may also 
be removed by changing the position of the worm gear 
to bring an unused portion in contact with the worm. 
This requires some disassembling to bring steering gear 
arm (K) in proper position. Play between the eccentric 
bushing and steering arm shaft can only be remedied 
'by replacing and fitting a new bushing. 





































134 


CHASSIS 


secured to the steering wheel shaft. The steer¬ 
ing wheel, being mounted on the upper end of 
this shaft, turns the worm, which in turn drives 
a worm gear. The worm gear is made either 
of bronze or steel. 

On any worm and wheel drive, regardless of 
its application, there is an end thrust. Con¬ 
sequently, end thrust bearings are provided 
at each end of the worm. The thrust bear¬ 
ings are generally of the ball thrust type, 
but they may be thrust plates instead. 

To adjust the worm to compensate for 
wear, an adjusting nut is usually provided, 
which may be located at either end of the 
housing, but is usually at the top. By turn¬ 
ing this adjusting nut inward, the end play is 
reduced. The end thrust adjusting nut is 
locked by means of a clamping lug. The 
clamping lug, which is part of the steering 
gear housing, is split for a short distance, thus 
allowing a clamping bolt to contract the hous¬ 
ing around the adjusting nut. 

The worm gear has a keyed shaft pressed 
into it,, which is termed the steering gear shaft, 
and is usually mounted in two bronze bearings. 
These bearings are, in most cases, eccentric; 
that is, the hole in them is offset from the 
center. The eccentric bushing is an adjust¬ 
ment to bring the worm gear closer to the 

worm. 

The steering wheel, to have the right amount 
of play and to be adjusted properly, should 
swing from one-half to two inches, rim meas¬ 
urement, before the road wheels respond. 
More play than this will allow the car to fol¬ 
low the ruts too easily, causing hard steering, 
while play of less than one-half inch results in 
unnecessary wear in the different parts of the 
steering device. 

Before adjusting the steering wheel to re¬ 
duce play, the complete steering mechanism 
should be examined to determine the location 
of the play, and what worn parts are causing 
this play. It may not always be in the steering 
device proper, but may be caused by any of the 
connecting parts. 

In time, the teeth of the worm gear become 

worn, and in this case the eccentric bushing 
may be turned so the gear meshes closer 
to the worm. Eventually, the limit of adjust¬ 
ment by this method is reached; that 
is, when the eccentric bushing is moved 
around one-half revolution, or 180°, the worm 
gear is moved as close to the worm as pos¬ 
sible by this adjustment. It is advisable, under 
these conditions, to change the mesh and 
bearing position of the teeth. This is possible 
because in ordinary steering only the lower 
half of .the threads of the worm are in con¬ 
stant use. The upper half of the threads re¬ 


ceives very little wear. The above mentioned 
adjustment is made by disassembling the de¬ 
vice and meshing the worm and worm wheel 
in a new position. 

Play in the radial bearings or bronze bush¬ 
ings of the worm shaft is eliminated by the 
replacement and refitting of new bearings. The 
new bearings, after they are pressed in, may 
be reamed to the correct fit. 

The end of the worm gear shaft outside the 
housing is square. The steering gear arm has 
a square hole machined in it. One side of the 
arm is split and provided with a clamping 
screw which passes through part of the worm 
gear shaft on which the arm is mounted. 
There is a small notch cut in the squared end 
of the shaft to accommodate the bolt or screw. 
The bolt engages with the notch and prevents 
the steering gear arm from coming off the 
shaft. 

The worm and worm gear are enclosed in 
either a cast iron or aluminum housing. The 
housing may be either a single casting or 
of the divided type. The divided type is held 
together by screws or bolts. The housing 
should be filled with grease or heavy oil, and 
has an oil filling cup or plug on the upper side 
for this purpose. It is necessary to keep the 
steering device well lubricated. 

Worm and Sector Steering Device 

The worm and sector steering device is 
usually constructed similar to the worm and 
worm gear, except that instead of using a 
complete worm gear, only a section is em¬ 
ployed, usually about a ninety degree sector. 

The sector may be enclosed entirely in a 
housing and lubricated the same as the 
worm and wheel type, or the housing may be 
of a web construction. The latter construc¬ 
tion causes rapid wear, due to the lack of 
lubrication, as the lubricant will have to be 
placed on the surface by hand, in which case, 
it soon loses its proper lubricating quality from 
contamination by sand and dust. The adjust¬ 
ments are the same as in the worm and wheel 
type. 

Split Nut Type (Jay-Cox) Steering Device 

The split nut type steering device has a worm 
on which is machined both a right and a left 
hand thread. This worm is hardened and 
ground to reduce wear. Two half nuts made 
of bronze, one having a right and the other 
a left hand thread, are in mesh with the threads 
on the worm. The outer surface of the nut 
bears against the inside wall of the housing. 
When the steering wheel and worm are turned, 
one nut moves up and the other moves down. 
Reversing the steering wheel also reverses the 
direction of the movement of the half nuts. 



STEERING DEVICES 


135 


Fastened on the bottoms of these bronze 
half nuts are hardened steel plates, upon 
which the rollers on the rocker arm rest. The 
rocker arm is mounted on a shaft in the lower 
end of the housing at right angles to the worm. 
On the square end of this shaft the steering 
gear arm is mounted. Turning the steering 
wheel in one direction, moves the right hand 
half nut down, pushing the rocker arm with it, 
while the left hand half nut moves up with the 
opposite end of the rocker arm. Turning the 
steering wheel in the opposite direction re¬ 
verses the movement of the half nuts, the 
rocker arm and the steering gear arm. 

In assembling this steering device the right 
and left hand nuts must be mounted on their 
proper sides. If the nuts are transposed in 
their mounting, it will reverse the action of the 
steering device. That is, when the steering 
wheel is turned in one direction, the steering 
arm is moved in such a way that the car turns 
in a direction opposite to the movement of the 
steering wheel. 


The only adjustment provided on this steer¬ 
ing device is the end play adjusting nut which 
is usually clamped into the housing with a 
clamping bolt, similar to the other steering 
devices. The thrust bearings provided are 
usually of the ball thrust type. 

When assembling this steering device, mount 
the nuts with the hardened plate ends against 
the rocker arm rollers. 

The housing on this steering device is pro¬ 
vided with a grease filling plug and should be 
kept full of grease at all times. 

Worm and Nut Steering Device 

The worm and nut steering device is con¬ 
structed with a right hand thread on the worm. 
Mounted on the worm is a nut with a connect¬ 
ing link. This link connects with a crank 
arm on the steering gear shaft, the latter be¬ 
ing mounted in the housing at right angles to 
the worm. The nut moves up and down and 



FIG. 99 

SPLIT NUT STEERING GEAR 


A. Right and left hand thread worm. 

B. Left hand half nut. 

C. Right hand half nut. 

D. Steel roller. 

E. (Steering gear arm. 

F. Rocker arm. 

G. Steering gear shaft. 

H. Hardened steel plate. 


I. Ball end. 

J. Grease filler plug. 

K. Thrust bearing. 

L. End play adjusting nut. 

M. Adjusting nut clamping lug. 

N. Steering wheel shaft. 

O. Steering column tube. 


The adjustment on this type of steering device is the 
end play adjusting nut (L). This nut adjusts the end 
play in the worm and its connections. To remove the 
lost motion caused by the end play in the worm, loosen 
the screw in the clamping lug (M), move the nut inward 
until the bearings are tight, back the nut away a fraction 
of a turn so as to give the thrust bearing a little clear¬ 


ance, tighten the bolt in the clamping lug and lock it. 
The ball thrust bearing may wear, as may also the 
threads on the half nuts, the surfaces of the half nuts 
that rub on the wall of the housing, the hard steel 
rollers, roller pins and the steering arm shaft and bear¬ 
ings. The housing should be packed with light cup 
grease for lubrication. 





































































136 


CHASSIS 





















































































STEERING DEVICES 


137 


FIG. 100 

WORM AND NUT STEERING DEVICE 


A. Steering wheel rim. 

B. Steering wheel spider. 

C. Horn button. 

D. Spark hand lever. 

E. Throttle hand lever. 

F. Spark and throttle sector arm. 

G. Shaft bearings. 

This sketch shows a conventional 
mounting of the control rods or 
tubes through the center of the 
steering column. The standard 
number of tubes for a steering de¬ 
vice in which the conti'ols extend 
through the center is five—two sta¬ 
tionary and three movable. 

The outer tube is called the 
steering column tube, and is fas¬ 
tened rigidly to the stationary case 
or housing (Q). The next is the 
ste'ering wheel tube (or shaft). At 
the top of this tube the steering 
wheel spider (B) and rim (A) are 
fastened on with keys and a nut. 
Mounted just below the wheel 
spider and within the outer or 
stationary tube is a plain roller 
bearing which takes the radial load 
of the steering wheel and shaft. 

On the lower end of the steering 
wheel tube is a screw thread or 
worm (I) provided with bearings 
(G). This worm or screw thread 
(I) actuates the nut (J), which in 


H. Grease filler plug. 

I. Worm. 

J. Worm nut. 

K. Steering gear shaft. 

L. Steering gear arm. 

M. End play adjusting nut. 

N. Cover. 

turn operates the steering arm (L) 
through the connecting link (S) 
and crank arm (T). When the 
steering arm is moved back and 
forth, there is an end thrust on 
the nut, worm and steering tube. 
This thrust is taken by the tap¬ 
ered roller hearings (G), which 
also take the radial load. In some 
devices of this type, a plain bronze 
bushing takes the radial load and 
two ball thrust bearings take the 
thrust load with the adjusting nut 
at the top as in the worm and wheel 
device. The third tube from the 
outside is called the spark and 
throttle sector tube. This tube is 
held stationary with the housing 
at the lower end by an adjuster, 
which is threaded into the cap (N) 
with a packing between the tube 
and case to prevent oil leakage. 
At the top of this stationary tube 
the spark and throttle sector (F) 
is mounted. 

At the top of the fourth tube 
from the outside, the throttle hand 


O. Throttle tube lever. 

P. Spark tube lever. 

Q. Steering gear case. 

R. Steering gear case cover. 

S. Connecting link. 

T. Crank arm. 


lever (E) is mounted. Moving this 
hand lever moves the throttle tube 
lever (O), which is connected to 
the throttle valve of the carburetor. 
This fourth tube is called the 
throttle hand lever tube. 

The inner tube is called the spark 
lever tube. At the top of this tube 
the spark lever (D) is fastened. 
Moving this hand lever moves 
the spark tube lever (P), which in 
turn operates the spark advance 
lever of the breaker mechanism. 
The horn wire, which connects the 
horn button (C) with the horn, 
passes through the center of this 
tube. 

To remove play of the w'orm and 
wheel tube in the housing, remove 
lever (O) and lever (P), also pack¬ 
ing nut and cap (N). Screw the 
adjusting nut (M) forward, forcing 
the outer race of the tapered roller 
bearing forward and downward. 
This adjusts for both radial and 
thrust play. 


through the connecting link and crank, moves 
the steering gear shaft and steering gear arm 
backward and forward. 

This steering device is provided with an ad¬ 
justing nut to take up the end play. The hous¬ 
ing should be packed with grease to reduce the 
amount of friction and wear. 

Worm, Screw and Nut Type 

There is also a worm, screw and nut steer¬ 
ing device, which has a worm with a left hand 
thread on the outside and a right hand thread 
on the inside. A screw^ with a right hand 
thread is mounted within the w’orm. The 
screw projecting outw’ard fits into one end 
of a rocker arm fastened on a shaft 
that is mounted at right angles to the worm. 
A nut with a left hand .thread is mounted on 
the outside of the worm. The nut is connected 
to the other end of the rocker arm. When the 
steering w^heel is turned the w^orm will turn, 
and this moves the screw inw'ard and the nut 
outw’ard, thus causing the rocker arm shaft 
and steering gear arm to move. This device 
is provided with an end thrust bearing and an 
end play adjusting nut. No other adjustments 
are provided. 


Planetary Steering Device 

The tw^o main points of difference betw'een a 
planetary type and others are: first, the drive is 
by planetary action through spur gears instead 
of through a w'orm. The other is that the 
movement of the steering gear arm is parallel 
with the axle, crosswise of the car, instead 
of back and forth, parallel with the frame. 

The Ford steering device is of the plane¬ 
tary type. It consists of five gears; one is a 
large internal stationary gear on which the 
teeth are cut on the inner instead of the outer 
face. This internal gear, w^hich has thirty-six 
teeth, forms a part of the steering gear case 
or housing. 

There is a three-pronged spider fastened to 
the top of the steering gear post, w'hich con¬ 
tinues through the steering gear housing and 
has the steering gear ball arm fastened to it at 
the bottom. On this spider are mounted three 
gears having twelve teeth each, w^hich are 
called the planet gears. The steering wheel is 
keyed to the steering w'heel shaft on which is 
cut a small gear with tw^elve teeth, called 
the sun gear. On the interior of the steer¬ 
ing gear post is a bronze bushing in w^hich 
the end of the steering wheel shaft rides. 





138 


CHASSIS 


















































































































































































































































STEERING DEVICES 


139 


FIG. 101 

FORD PLANETARY STEERING DEVICE 


A. Steering wheel rim, 

B. Wheel nut. 

C. Steering wheel spider. 

D. Sun gear. 

E. Planet gear. 

F. Spider pin. 

G. Internal stationary gear. 

This sketch shows a partial cross- 
sectional view of the planetary 
steering device (Ford). There is 
no adjustment provided on this de¬ 
vice to compensate for wear. Worn 
gears or pins should be replaced 
with new parts. 


H. Cover. 

I. Bearing bushing. 

J. Gas control lever. 

K. Spark control lever. 

L. Steering column tube. 

M. Steering shaft. 


If the bearing (I) wears, it Can 
be split with a chisel and removed. 
Then press in a new bushing. Play 
at the lower end, where the steer¬ 
ing shaft passes through the 
bracket, can be remedied by press- 


N. Supporting bracket. 

O. Grease cup. 

P. Steering gear arm. 

Q. Gas control lever arm. 

R. Spark control lever arm. 

S. Quadrant. 


ing in a thin bushing. It may be 
necessary to ream the bracket out 
slightly in order to press a bushing 
in. Wear at this point is greatly 
reduced by lubrication supplied 
through the grease cup (0). 



FIG. 102 

PLANETARY GEAR ASSEMBLY 


A. Spider pins. D. 

B. Sun gear. E. 

C. Planet gears. 

This sketch shows an end view of the gear assembly 
employed in the planetary steering device (Fig. 101). 
The steering wheel is fastened to the shaft on which the 
sun gear (B) is cut. 

When the steering wheel and the sun gear (B) are 


Spider. 

Internal stationary gear. 


turned, the planet gears (C) revolve on their axes and 
at the same time travel around on the internal sta¬ 
tionary gear. This drives the spider and the steering 
gear ball arm in the same direction in which the steer¬ 
ing wheel and sun gear are turned. 





140 


CHASSIS 


There is no connection between the steering 
wheel shaft and the steering gear post and 
spider except through the gears. 

When the steering wheel is turned, the center 
gear of twelve teeth turns with it. This gear 
is in mesh with the three planet gears and 
causes them to revolve on their own axes. The 
three planet gears are meshed with the large 
stationary internal gear of thirty-six teeth; 
by holding the thirty-six tooth gear stationary 
and turning the center twelve tooth sun gear, 
the three twelve tooth planet gears in revolving 
on their own axes will travel forward, using 
the interior of this large gear as a track. 

The spider turns in the same direction as the 
steering wheel. The planetary action of the 
gears and spider causes the steering wheel to 
travel a greater distance or faster than the 
spider and steering gear ball arm. 

When the steering wheel makes one com¬ 
plete revolution on its own axis, the planet 
gears do not make a complete revolution on 
their axes, but travel forward on the outer 
gear nine teeth instead of twelve, the differ¬ 
ence being caused by the forward travel of the 
spider. If the spider was held stationary and 


the thirty-six tooth gear was free to revolve, 
in one revolution of the steering wheel the 
planet gears would revolve twelve teeth or one 
complete revolution on their axes. 

The difference in the distances traveled by 
the steering wheel, planet gears and spider is 
due to the fact that the planet gears are travel¬ 
ing forward on the outside of the center gear, 
using the thirty-six tooth gear as a track. In 
one revolution of the center gear which is con¬ 
nected to the steering wheel, the spider moves 
forward one-quarter of a revolution. In order 
to make the spider travel a complete revolu¬ 
tion, the steering wheel must necessarily make 
four revolutions. 

This device is not adjustable. To take up any 
lost motion or play in the steering device, it is 
necessary either to put in new planet gear pins 
on which the planet gears revolve, or put in 
new gears. There is no end thrust in this de¬ 
vice to necessitate the use of a thrust bearing. 
The bearing at the end of the steering wheel 
shaft, which is made of bronze, can be re¬ 
placed. 

The housing in which these gears are 
mounted should be packed with grease. 



steering wheel key and nut. 
Steering gear thrust bearing. 
Steering gear arm on shaft. 
Ball and socket joint. 
Steering knuckle pivot bolt. 
Tie rod ends. 

Wheel bearings. 


FIG. 103 


POINTS FOR ADJUSTING LOST MOTION IN 
THE STEERING ASSEMBLY 







STEERING DEVICES — CLUTCHES 


141 


GAS AND SPARK CONTROL LEVERS 

The gas and spark control levers are mounted 
on a sector at the top of steering column, either 
just above or below the wheel spider. The por¬ 
tions of these levers that are parallel to the 
steering column may be either shafts or tubes, 
and may be mounted in brackets on the out¬ 
side of the steering column or pass through 
the center of the steering column. One lever 
operates the spark advance and retard mech¬ 
anism, and the other operates the throttle 
valve on the carburetor. Both the spark lever 
and the gas lever may move downward to ad¬ 
vance the spark and open the throttle valve 
or both move upward. Sometimes both are on 
the same side, either moving downward or up¬ 
ward. 

A foot operated lever is also used to control 
the movement of the throttle valve. It is called 
the foot accelerator. The connections between 
these levers are so arranged that moving the 
gas control lever at the steering wheel also 
moves the foot accelerator, but moving the 
foot accelerator does not move the gas con¬ 
trol lever at the steering wheel. To open the 
throttle valve with the foot accelerator, press 
it downward or forward. 

To distinguish the gas lever from the spark 
control lever when they are not marked, pro¬ 
ceed in the following manner: Knowing that 
the movement of the foot accelerator forward 
or downward opens the throttle valve, then 
move the gas control lever at the steering 
wheel in the direction that moves the foot 
accelerator upward. Continue to move the gas 
control lever in that direction until the foot 
accelerator is all the way up. This is the closed 
position of the throttle valve, and in all cases 
the spark lever is in the same relative position 
for a fully retarded spark. Moving the spark 
lever will not move the foot accelerator. 

The spark lever and gas lever always 
move in the same relative direction for ad¬ 
vancing the spark and opening the throttle 
valve. This is mentioned because when car¬ 
buretors are changed, care should be taken to 
see that moving the gas control lever in the 
same direction as formerly, opens the throttle 
valve. This mounting and action should never 
be reversed. If it does not work the same as 
formerly, put in an extra bell crank. 

CLUTCHES 

In the study of the internal combustion en¬ 
gine it was shown that the operation depended 
upon power developed within itself, and that 
it had to be started by some external means. 
It is one of the fundamental points in the gas 
engine that the power developed bears a very 
important relation to the speed of the engine. 


'It must attain a certain amount of speed and 
momentum in order to overcome the effect of 
any load when it is applied; also in using the 
automobile, there are many times when it is 
desired to stop the car without necessarily 
stopping the engine. 

It is the purpose of the clutch to meet these 
conditions, and it is placed between the engine 
and the transmission system to permit the 
connecting and disconnecting of those two 
units at the will of the operator. In accom¬ 
plishing this, it is very necessary that the 
engine should be engaged with as smooth and 
gradual an action as possible, to avoid too 
sudden an application of a heavy load, which 
might stop the engine, also to prevent undue 
strain on all parts of the car, and jerky 
or uncomfortable riding. Thus one of the 
important requisities of the clutch is flexibility. 

To obtain this flexibility, provision must be 
made to allow the clutch to slip. That is, the 
flywheel or driving member will turn faster 
than the driven member until the car is under 
motion, after which the clutch should cease to 
slip. 

Clutches are made in several types, as 
follows: 

Cone: 

r Lubricated 
Disc: j 

[ Dry 

Plate. 

CONSTRUCTION 
Cone Clutch 

Single Spring (Fig. 104): 

The flywheel is fastened rigidly to the crank¬ 
shaft and acts as the driving member. The 
inside of the flywheel is machined smooth and 
at an angle. On an extension of the crank¬ 
shaft, which is called the tail shaft, the driven 
member is usually mounted. The driven mem¬ 
ber is termed the cone, and the outside sur¬ 
face is machined at the same angle as the in¬ 
ner surface of the flywheel. 

A leather facing is fastened on the cone with 
copper rivets. Mounted in the face of the cone 
and resting against the inside of the leather 
facing are usually a number of small springs 
called insert or clutch facing springs. The 
purpose of these springs is to raise the leather 
facing in several spots and prevent the full 
surface of the facing from coming in contact 
with the flywheel when engaging the clutch, 
thus eliminating grabbing. 

A bronze bushing is pressed into the cone, 
which carries the radial load of the driven 
member when the clutch is disengaged. The 
clutch spring (a heavy coil spring )is mounted 


Single Spring. 
Multiple Spring. 




142 


CHASSIS 



A. Crankshaft. 

B. Flywheel flange. 

C. Flywheel. 

D. Clutch cone. 

E. Clutch facing spring and plunger. 

F. Grease cup. 

G. Oil hole. 

H. Clutch spring. 

I. Clutch cone bushing. 


J. Tail shaft. 

K. Clutch thrust bearing. 

L. Clutch spring adjusting nut. 

M. Splined driving hub. 

N. Clutch release bearing housing. 

O. Retainer nut. 

P. Clutch brake. 

Q. Clutch shaft with splined end. 


FIG. 104 


To disassemble, remove the trans¬ 
mission from the clutch, remove 
the bolts that hold the driving 
hub (M) on the clutch, then remove 
the cotter pin and nut (L). This 
will allow the spring and the cone 


CONE CLUTCH—SINGLE SPRING 

to be removed. 

When refacing the cone, tighten 
the insert spring plunger nut which 
holds the spring and plunger com¬ 
pressed. After the facing is riveted 
on, loosen this nut and allow the 


spring and plunger to force the 
facing away from the cone when 
the clutch is disengaged. The 
larger nut acts both as a guide for 
the plunger and as the spring ad¬ 
juster. 











































































































































143 


CLUTCHES 



FIG. 105 


CONE CLUTCH—MULTIPLE SPRING 


A. 

Crankshaft. 

J. 

Clutch release bearing housing. 

B. 

Crankshaft bearing. 

K. 

Clutch release thrust bearing. 

C. 

Clutch facing—leather. 

L. 

Clutch release sleeve. 

D. 

Clutch cone. 

M. 

Splined clutch shaft. 

E. 

Clutch spring. 

N. 

Inspection plate. 

F. 

Clutch spring nut. 

O. 

Tail shaft bearing bushing. 

G. 

Clutch spring spider. 

P. 

Clutch facing rivets (copper); 

H. 

Thrust bearing. 

Q. 

Flywheel. 

I. 

Clutch thrust bearing retainer. 

R. 

Flywheel flange. 



S. 

Crankcase. 
































































































































































144 


CHASSIS 


around the tail shaft and is usually held in 
position by an adjusting nut with a ball thrust 
bearing mounted against the spring to take 
the thrust strain when engaging or disengag¬ 
ing the clutch. 

Multiple Spring (Fig. 105): 

The construction of the multiple spring cone 
clutch is the same as a single spring, with the 
exception of the mounting of the clutch spring. 
A separate spider is mounted on the tail shaft, 
which is held in position by a retaining nut 
with a ball thrust bearing to take the thrust 
strain. 

The radial load of the spider is taken by the 
cone member. The clutch springs are mounted 
upon the spider pins or studs outside the cone. 
The springs are held jn place by either ad¬ 
justing nuts or retainers. 

These clptch springs are farther away from 
the center of the shaft, permitting the use of 
several light springs instead of one heavy 
spring as on the single spring type. By having 
the spring as close to the clutching surface as 
possible, the multiple spring clutch is easier to 
disengage than the single spring type. The 
clutch springs, being mounted on the outside, 
are more accessible and easier to adjust. 

The clutch shaft extends through the cone 
member, and is fitted with a bushed bearing in 
which the tail shaft runs. 

Disc Clutches 

The disc clutch consists of two sets of an¬ 
nular discs, one set of driving discs and one 
set of driven discs. They are placed together 
in alternate order each driven disc being lo¬ 
cated between two driving discs. The driv¬ 
ing discs are provided with keys or slots on 
their outer circumference which fit in to slots 
or keys on the inside of a drum-shaped hous¬ 
ing secured to the flywheel or fit over studs 
secured to the flywheel. The driven discs are 
fitted with lugs or keyslots on their inner cir¬ 
cumference, or fit over studs, either of which 
places them in connection with a drum on, 
or secure them directly to, the driven shaft. 
Generally there is one more driving disc than 
there are driven discs making the two out¬ 
side discs of the same kind. The drum carry¬ 
ing the driven discs has a flange at one end 
which forms a stop for the discs, and the other 
end is a spider or pressure plate against which 
the clutch spring exerts its pressure. 

The number of discs required is dependent 
upon several things. The power to be de¬ 
livered by the engine determines the amount of 
frictional area and the clutch spring pressure 
required, and yet the amount of work done by 
the operator in disengaging the clutch must be 
taken into consideration in proportioning the 
various units. 


An extension on the driven drum or shaft is 
supported in the driving member by a bronze 
bushed bearing or a ball bearing to take the 
radial load. Disc clutches are made in two 
types lubricated and dry. 

Lubricated Disc Clutches 

In the lubricated clutch the discs are gener¬ 
ally made of saw steel about 1/16" thick. 
Saw steel is selected because of its being hard¬ 
ened and of more uniform thickness than or¬ 
dinary sheet steel. In some clutches one set 
of discs is of bronze, and in others sheet copper 
is used. Clearance between the discs when dis¬ 
engaged varies from 1/64" to 1/100". 

One set of discs is sometimes provided with 
cork inserts. The cork is quite compressible, 
and it is customary to make the cork plugs of 
such a size that when free they project about 
1/16" above the surface of the metal plate. 
When the discs are forced together the contact 
is between metal and cork only and owing to 
the compressibility of the cork the engage¬ 
ment will be very smooth. When the full pres¬ 
sure of the spring is applied, the surfaces of 
the cork are compressed flush with the plate 
surface. The cork usually covers from 25% to 
50% of the area of the discs. 

The clutch spring arrangements for engag¬ 
ing the discs in this type clutch are both sin¬ 
gle and multiple, similar to those used on the 
cone type clutch. The distinct advantage of 
the disc clutch is that the amount of frictional 
surface can be made much greater than on the 
cone clutch, and the frictional force per unit 
of surface will be much smaller. 

The bath of oil in which the lubricated disc 
clutch runs, serves two purposes; first to lubri¬ 
cate the face of the discs when disengaged, and 
second to assist in making a smooth applica¬ 
tion of power. When the clutch is thrown in, 
the film of oil is gradually squeezed out per¬ 
mitting a very easy and gradual engagement. 
The cork inserts provide greater friction in 
engaging the clutch and also have the advant¬ 
age of protecting the discs from scoring in 
the absence of proper amount of lubricant. 

The clutch is enclosed in an oil tight hous¬ 
ing and may be lubricated directly from the 
engine or separately. When lubricated separ¬ 
ately, manufacturers recommend a mixture 
of machine oil or gas engine oil and kerosene. 
The thinner the lubricant the better the clutch 
will hold, while the more viscous the lubricant 
the more gradually it will pick up the load. 
The kerosene should never be used when the 
clutch is lubricated from the engine. 

The weak point of the lubricated disc clutch 
is its tendency to drag if the oil in the housing 
is not suitable for the purpose, or if too much 
is introduced. 



CLUTCHES 


145 


Dry Disc Clutch 

In the dry disc clutch one set of discs is 
either faced with asbestos fabric on both sides 
or else provided with cork inserts. Both of 
these materials when used with steel have a 
much greater frictional contact than steel or 
bronze on steel. 

The asbestos facing is a fabric composed 
very largely of asbestos fibre and containing 
some brass wire and cotton to give it the 
necessary strength. The asbestos is used on 
account of its good frictional qualities and its 
resistance to heat. It is usually secured to the 
metal discs by means pf rivets, and is used on 
both sides of alternate discs only. The rivets 
must be countersunk to be sure of no metal 
contacts as that would destroy the frictional 
qualities. 

Plate Clutch 

The plate clutch consists of three discs or 
plates only and is used without lubricant. The 


plates are of cast iron and bronze or cast iron 
and steel. Since there are only two friction 
surfaces, it is necessary to use rather large 
plates and multiply the pressure of the clutch 
spring by using levers or toggle mechanism, 
as illustrated in Fig 111. 

CLUTCH BRAKE 

In engaging the transmission gears for start¬ 
ing the car or changing the speed, it is neces¬ 
sary that both the shaft driven by the clutch 
and the sliding or change gears of the trans¬ 
mission be either stationary or running at ap¬ 
proximately the same speed in order that they 
may engage quietly and without damage. 

It is the purpose of the clutch brake to stop 
the revolving driven member or decrease its 
speed so that the gears may be properly en¬ 
gaged. It is a stationary member, mounted so 
that when the clutch is disengaged, the driven 
member, which is revolving from the momen¬ 
tum received from the fiywheel, will come 

(Continued on Page Ji9J 




4 5 6 


FIG. 106 


CLUTCH DISCS 


(1) 

A. 

Clutch driven drum. 


C. 

Clutch driven disc stud. 

E. 

Driving disc. 

B. 

Driving groove. 


E. 

Driven disc. 

H. 

Cork insert. 


E. 

Driven disc. 

(4) 

A. 

Clutch driving drum. 

(6) A. 

Clutch driving drum. 

(2) 

A. 

Clutch driven drum. 


D. 

Clutch driving teeth. 

B. 

Driving key. 

B. 

Driving key. 


E. 

Driving disc. 

E. 

Driving disc. 


E. 

Driven disc. 

(5) 

A. 

Clutch driving drum. 

F. 

Asbestos facing. 

(3) 

A. 

Clutch driven drum. 


B. 

Driving groove. 

G. 

Copper rivets. 





146 


CHASSIS 



FIG. 107 























































































































































































































































CLUTCHES 


147 


FIG. 107 

DRY DISC CLUTCH—SINGLE SPRING 


A. 

Crankshaft. 

1. 

Clutch brake lever. 

B. 

Flywheel. 

J. 

Clutch brake facing. 

C. 

Driving drum. 

K. 

Clutch spring. 

D. 

Driven drum. 

L. 

Pressure plate. 

E. 

Clutch shaft. 

M. 

Clutch release hub plate. 

F. 

Ball thrust bearing. 

N. 

Clutch shaft bearing. 

G. 

Clutch release collar. 

0. 

Driving discs. 

H. 

Clutch release fork. 

P. 

Driven discs. 


In this clutch the release fork 
(H) moves forward and with it 
(M) and (L), thereby disengaging 
the discs from the power. To move 
the clutch pedal and release fork 


forward, necessitates a double lever 
and connecting link action. As the 
release fork (H) is moved for¬ 
ward, the hub plate (M) engages 
with the flexible clutch brake, re¬ 


ducing the speed of the transmis¬ 
sion countershaft and allowing the 
gears to slide into mesh more 
easily. 



-Fl(^ i^^heel 
C/o^mc^ spnn^f 


Dr//e t>u^/7incf 
Thrust member 
O// t?ear/mf here 


Rehef co//ar 
Thrust masher 




/- 

0//er 

Dust masher 

Graphite bronze bushmp 
Thrust beanmp 
Dr I yen (^ear 
'Larc^e <t/sc and fact hip 
Gma// d/sc 
T/i/ mhee/ hub 


FIG. 108 

DRY DISC CLUTCH, MULTIPLE SPRING 

























148 


CHASSIS 


Driven key. 

Driving disc. 

Driving key. 

Thrust bearing. 

Pelt washer. 

Clutch release fork. 

Clutch shaft flange. 

Woodruff key. 

Clutch spring. 

Tail shaft bearing. 

Driven drum hub bearing bushing. 



FIG. 109 

LUBRICATED DISC CLUTCH—SINGLE SPRING 


OPERATION 

As the clutch pedal is pressed forward, the fork 
(F) moves the flange (G) and shaft back, and with it 


(A), thereby disengaging the discs. As the clutch pedal 
comes back, the spring (I) will press the discs together 
again. 
































































































































































































CLUTCHES 


149 


in contact with the brake, thus retarding its 
motion. The conditions existing when starting 
the car give the best demonstration of the 
necessity for the brake. The gear driven by 
the clutch shaft may possibly be revolving 200 
R. P. M. when the clutch is disengaged, while 
the transmission gears are not in motion at all. 

CLUTCH OPERATION 

Cone type clutch —To disengage the clutch, 
a clutch release fork or shifting yoke is pro¬ 
vided, which is mounted around the driven 
member and operated by the clutch pedal. 
Pushing the clutch pedal forward forces the 
driven clutch member backward, since the 
clutch pedal fulcrum is above the release fork. 
The clutch normally stands engaged. With 
few exceptions there is no provision made to 
lock or hold the clutch disengaged when the 
driver removes his foot from the clutch pedal. 
The clutch spring will engage the clutch when 
the pedal is released. 

When engaging the clutch, the clutch spring 


is allowed to force the driving and driven mem¬ 
bers in contact with each other. 

Suppose the transmission gears are in neu¬ 
tral; pressing the clutch pedal forward moves 
the driven member back out of contact with 
the driving member. 

After the transmission gears are engaged, 
the clutch must be engaged to transmit the 
power from the engine to the rear wheels. 
When the clutch is disengaged, the small insert 
springs force the clutch facing away from the 
cone, so that as the clutch pedal is allowed to 
move back slowly, only a small surface of the 
clutch engages with the flywheel. The clutch 
facing at the points where the insert springs 
are mounted is the first to come in contact with 
the flywheel. The friction between the two 
members causes the driven member and the 
rear wheels to start revolving slowly. 

As soon as the car is in motion, the clutch 
nedal should be allowed to move all the way 
back, which allows the full pressure of the 
clutch spring to overcome the pressure of the 


OSAR SHIFT LEVER 


BEARING retainer 
CLAMP BOLT 

TRANSMISSION 
DRIVE PINION 

HIGH AND INTERMEDIATE 
SLIDING GEARv 

GEAR SHIFT FORKS- 

LOW AND REVERSE 
SLIDING GEAR- 

MAIN TRANSMISSION- 
' SPLINE 5HAFT 

GEAR SHIFT ROD- 

BEARING RETAINE: 


EMERGENCY BRAKE LEVER 


CLUTCH PEDAL 



TRANSMISSION 
NEUTRAL LOCK , 


SPEEDOMETER 
DRIVE GEAR 
'HOUSINGS 


TOGGLE LEVER 
COLLAR 


REVERSE 
IDLER GEAR-1 


COUNTERSHAFT 
REVERSE GEAR' 

COUNTERSHAFT 

LOW GEAR- 

COUNTERSHAFT 

INTERMEDIATE GEAR' 


LUTCH SHIFTER 
TOGGLE LEVER 


CLUTCH TOGGLE 
PLATE 


COUNTERSHAFT GEAR^ 

FLEXIBLE DISC. COUPU»G--' 

FIG. 110 


CLUTCH COVER 
CLUTCH THROWOUT BEARING 


\ 


DRY PLATE CLUTCH AND TRANSMISSION 


































































150 


CHASSIS 



FIG. Ill 







































































































































CLUTCHES 


151 


Clutch drive pin. M. 

Clutch driven plate. N. 

Clutch Raybestos disc. O. 

Clutch bell crank pins. P. 

Clutch cover. Q. 

Clutch thrust ring, or driving plate. R. 

Clutch thrust collar. S. 

Clutch release bearing. T. 

Clutch release sleeve. U. 

Clutch spring. V. 

Clutch brake. \V. 

Clutch release fork. 


Felt washer. 

Clutch gear. 

Clutch shaft. 

Flywheel. 

Clutch adjusting ring. 

Clutch adjusting screws (or slot bolts). 
Clutch shaft ball bearing. 

Crankshaft. 

Clutch shaft bearing. 

Inspection plate opening. 

Clutch bell crank, or pressure levers. 


A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

J. 

K. 

L. 

To adjust the clutch; first dis¬ 
engage it, remove the inspection 
plate (V) and loosen the slot bolts 
(R). In the position shown, one 
slot bolt can be loosened. Then 
by turning the flywheel one-half a 
revolution, the other slot,bolt (R) 
will be on top and can be* loosened. 
The next step is to move the slot 
bolts (R) clockwise about one-half 
an inch. 

Engage the clutch, and if the dis¬ 
tance between the clutch cover and 
the face of the clutch release bear¬ 
ing retainer face is less than 2^", 
again disengage the clutch and tap 
the slot bolts back counter clock¬ 
wise until this space is 2^". This 
adjustment also adjusts the foot 
pedal, and when the clutch slips it 
is usually due to the clutch pedal 
striking against the under side of 
the floor board. 

When adjusting the clutch, see 
that at least V 2 " clearance is left 
between the pedal and foot board 
for clearance. If the pedal hangs 
on the under side of the foot board, 
use the clutch adjustment only for 
obtaining the necessary clearance, 
as the single clutch adjustment 
automatically adjusts the pedal. 
When the clutch is adjusted, the 
clutch pedal automatically moves 
forward, allowing the necessary 
clearance. 


FIG. Ill 

BORG & BECK DRY PLATE CLUTCH 
SINGLE SPRING 


The above adjustment can be fol¬ 
lowed when adjusting a new clutch, 
but does not always hold true on a 
clutch after it becomes worn. On 
the average car equipped with a 
Borg & Beck clutch, when the clutch 
slips, first examine the clutch pedal 
to see if it strikes the floor board 
when the foot is removed. If so, 
adjust the pedal to prevent this, 
without changing the clutch adjust¬ 
ment. If the pedal is clear of the 
floor board when the clutch is en¬ 
gaged, slippage may be caused by 
excessive oil on the facings or as¬ 
bestos discs; but the more common 
cause is worn facings. To remedy 
this, remove the inspection plate, 
loosen the two slot bolts, and tap 
the bolts clockwise about to 
an inch. Then tighten the slot 
bolts. Do not adjust the clutch too 
tight. If the distance between the 
clutch release bearing surface and 
the clutch brake is less than i/4", 
the clutch may drag due to 
only a partial disengagement. This 
may sometimes be remedied by ad¬ 
justing the clutch brake. The 
clutch pedal should move about one- 
half its full forward travel before 
the clutch brake is applied. 

If the clutch has been adjusted 
until the adjusting screws rest 
against the end of the cover slot, 
screw them out of their mounting 


holes and into the repeat holes ex¬ 
posed near the first end of the slot. 
This doubles the range of adjust¬ 
ment. When it is impossible to get 
further adjustment through the ad¬ 
justing screws, new friction rings 
will have to be installed. To do 
this, the clutch must be taken apart. 
First, disengage the clutch and 
place a block of wood between the 
clutch release bearing housing and 
the cover (E). This holds the 
spring compressed. Remove the 
clutch cover by taking out the cover 
screws which hold the cover onto 
the flywheel. Place a punch mark 
on the flywheel and the cover plate 
in order that they can be correctly 
assembled. Then remove the trans¬ 
mission and clutch shaft (O), 
spring (J), cover (E) and units 
attached (H), (I), (G), (D), and 
(W). 

Pull out the clutch thrust ring 
(F), then from the outside of the 
flywheel remove two of the drive 
pins (A) with a punch. This al¬ 
lows the removal of the clutch driv¬ 
en disc (B) and the inner and 
outer asbestos discs (C). After 
replacing new Raybestos discs, as¬ 
semble in the reverse order from 
which it was disassembled. Before 
assembling the clutch, examine the 
bearing (S) for wear, clean this 
bearing out well and pack with cup 
grease. 


small insert springs and forces the entire sur¬ 
face of the facing against the cone. 

After the clutch is fully engaged, there 
should be no slippage. Slippage in this case 
means that the flywheel turns faster than the 
driven member. The amount of spring pres¬ 
sure required for any clutch should be suffi¬ 
cient to hold the driven and driving members 
together tightly enough to prevent slippage 
when the clutch is engaged. If the clutch is 
not allowed to slip when it is being engaged, 
however, there would be an excessive strain 
placed on all the parts in the driving mech¬ 
anism. 


The flexibility of the cone clutch depends 
upon the spring inserts and clutch facing, 
which takes care of the friction and slippage 
necessary for a smooth engagement. 

Disc Clutch—The action of the disc clutch 
involves the same principles as explained 
above. In the dry type, the friction facing 
gives flexibility and takes care of the friction 
from the slippage when engaging, the same as 
the leather facing on the cone type. 

In the lubricated type, the oil between the 
driven and driving members prevents metal 
from coming in contact with metal, thereby 
reducing the friction. As the clutch is en- 




152 


CHASSIS 


gaged slowly, the power is applied from one 
disc to the other through the oil, instead of 
through a facing, as in the cone and dry disc 
types. 

The oil creates a drag with a certain amount 
of slippage, depending entirely upon how 
close the discs are together. 

The driven end of the clutch shaft which 
connects the clutch and the transmission is 
usually squared or splined. (A shaft that is 
splined has numerous keys on the outside of it, 
the metal between the keys being removed, 
instead of cutting the keyways in the shafts 
and inserting the keys, thus making a solid 
and strong construction). The purpose of this 
splined shaft is to allow for end movement of 
the driven member of the clutch and at the 
same time drive it. 

Troubles and Repairs 

Clutch troubles may be classified under the 
following headings: 

Slipping. 

Grabbing. 

Spinning. 

Dragging. 

Stuttering. 

Cone Type 

If the clutch slips after it is engaged the 
facing will soon become worn from the ex¬ 
cessive friction and high temperature. 

The cause of a slipping clutch may be: 

(1) Clutch spring tension weak. 

(2) Burned or worn clutch facing. 

(3) Warped cone. 

(4) Clutch facing oily or greasy. 

(5) Clutch shaft out of line. 

(6) Clutch release mechanism out of ad¬ 
justment. 

Remedies for slipping clutch: 

(1) To remedy weak tension of clutch 
spring, tighten the clutch spring adjusting nut. 
If no adjusting nut is provided, either the 
spring will have to be replaced or shims or 
washers inserted behind the spring. As a 
temporary remedy, wooden wedges may be 
driven in under the clutch facing. These 
should be removed as soon as possible for the 
facing will wear excessively at the high points. 

(2) To remedy a burned or worn clutch 
facing it will be necessary to replace the fac¬ 
ing. 

(3) A warped cone must be removed and 
replaced by new one. 

(4) Oily and greasy clutch facing may be 
remedied by washing the surface with kero¬ 
sene oil. A temporary remedy is to apply 
“Fuller’s Earth” or some form of talc to dry 
and absorb the oil. This should only be used 


in an emergency for if allowed to remain, it 
will cause the facing to become dry and then 
crack. 

(5) The breaking of a ball in the thrust 
bearing or tail shaft bearing may cause the 
clutch shaft to get out of a line. The remedy 
for this is replacemenOof bearing. 

(6) If anything interferes with the full 
movement of the clutch release yoke, clutch 
pedal or any of the parts of the clutch re¬ 
lease mechanism, it may prevent the clutch 
from fully engaging. Check up on all these 
parts and see that they are free to move the 
required amount. 

The cause of a grabbing clutch may be: 

(1) Too sudden engagement. 

(2) Clutch facing rivets projecting. 

(3) Clutch facing dry and hard. 

(4) Clutch facing spring improperly ad¬ 
justed. 

(5) Excessive tension on clutch spring. 

Remedies for grabbing clutch: 

(1) Too sudden engagement is caused by 
the operator letting clutch in too quickly. Use 
care release clutch pedal slowly and gradually. 

(2) If the clutch facing is badly worn the 
rivet heads may project above the surface of 
the facing and cause the clutch to grab when 
engaging. The rivets must be countersunk 
deeper and hammered down. The metal to 
metal contact first causes the grabbing then 
after the clutch is engaged may cause it to 
slip. 

(3) When the clutch facing becomes dry, 
hard and glazed it is not fiexible, and causes 
the clutch to grab. To remedy this, clean the 
glazed surface with emery cloth and apply 
as much Neatsfoot oil as the leather will ab¬ 
sorb. This softens the leather and makes it^ 
fiexible, restoring the life and texture of the* 
material. 

(4) If the clutch facing springs are not 
adjusted to force the facing away from the 
cone, the clutch will grab. The remedy is ad¬ 
justing the springs. This trouble may be par¬ 
ticularly noticeable after a new facing has 
been put on if the adjustment of these springs 
has been neglected. 

(5) Excessive tension on the clutch spring 
may make it impossible to obtain a smooth 
gradual engagement of the clutch. Remedy 
for this is to weaken the spring tension. 

A spinning clutch is one in which the driven 
member of the clutch continues to revolve for 
some time after the clutch is disengaged. This 
makes it very difficult to shift the transmission 
gears. A spinning clutch is due to the clutch 
brake being worn or out of adjustment. To 
remedy this, adjust or reface the clutch brake 



CLUTCHES 


153 



ENGINE, CLUTCH AND TRANSMISSION ASSEMBLY 

In this construction the oil that lubricates the engine 
also lubricates the clutch, transmission and the univer¬ 
sal joint. 



















154 


CHASSIS 


with fiber or asbestos so that the driven mem¬ 
ber of the clutch makes contact with the 
brake when the clutch pedal moves about one- 
half its travel forward, 

A dragging or sticking clutch is one in which 
the driven member continues to revolve even 
after the clutch pedal is pressed forward as far 
as it can move. The clutch will not be proper¬ 
ly disengaged even though the driven member 
is not in contact with the driving member. 
This may be caused by the bushing that is 
pressed into the cone or driven member fitting 
too tightly on the tail shaft. This is notice¬ 
able quite often on new cars, and will usually 
take care of itself after a certain length of 
time. If not, it can be remedied by removing 
the cone member and reaming the bushing to 
a running fit with an expansion reamer. 

It may be caused by improper lubrication of 
the tail shaft, or if the tail shaft should become 
bent or sprung out of alignment, it will cause 
the cone to stick and drag on this shaft. 

A stuttering clutch is one in which the clutch 
chatters and vibrates excessively. It may be 
caused by the fiywheel being out of alignment, 
or the bushing that is pressed into the cone 
becoming worn, which will cause the cone to 
have play on the tail shaft. This can be rem¬ 
edied by replacing with a new bushing. Lack 
of lubrication or lost motion at the clutch re¬ 
lease sleeve or clutch release fork also causes 
a stuttering clutch. This is remedied by lubri¬ 
cation and adjustment. 

Lubricated Disc Type 

This type of clutch has no exposed rivets, 
worn or dry facings, etc., and thus the 
majority of the common troubles are pre¬ 
vented. If the oil is too heavy, it may pre¬ 
vent the discs from making proper contact, 
causing clutch to slip. Remedy for this 
is to remove the oil, clean clutch with kero¬ 
sene and refill with grade of oil as recom¬ 
mended by car manufacturer or if clutch is 
contained in a separate housing lubricant may 
be thinned by adding a small amount of kero¬ 
sene. If clutch is lubricated from the engine 
oil supply, such change or thinning of oil is not 
possible: but grade of oil used in engine will 
seldom be heavy enough to give this trouble. 
NEVER add kerosene or a lighter oil to the 
clutch lubricant if it is supplied from the en¬ 
gine oil reservoir. The secret of efficient lubri¬ 
cated clutch operation is to use the correct oil 
recommended by the manufacturer of the 
automobile upon which the clutch is installed. 

Dry Disc Type 

Troubles of this type of clutch are practi¬ 
cally the same as cone clutch troubles. 


Dragging clutch may be caused by the driven 
member fitting too tightly on the tail shaft. 

Spinning clutch may be caused by a faulty 
clutch brake, although this is a trouble seldom 
found in a disc clutch. 

Grabbing clutch may be caused by exposed 
rivets, sudden engagement, worn facings or 
glazed and hardened facings. 

Slipping clutch may be caused by oil on the 
surface of the facing. Remove the oil by clean¬ 
ing with kerosene. Insufficient spring tension 
can be remedied by tightening the adjusting 
nut. 

Stuttering clutch is caused by play of the 
driven member on the tail shaft, or by the discs 
becoming loose in their mounting. This can 
be remedied by replacing with new parts. 

The correct sized facings for a disc clutch or 
cone clutch may be obtained from the manu¬ 
facturers. Always make sure that the rivet 
heads are below the surface of the facing. 

TRANSMISSIONS 

It is the purpose of the transmission to pro¬ 
vide means for varying the ratio between the 
speed of the engine and the speed of the car. 
Knowing that the engine develops more power 
at the higher speeds, it is necessary to have 
some means of connecting the engine at this 
high speed when the load conditions are heav>% 
such as starting the car or climbing a hill. It 
also provides means for reversing the direction 
of motion of the car, . 

Transmissions are made in three types; pro¬ 
gressive, selective and planetary. 

The progressive and selective types are 
made with three or four speeds forward and 
one reverse. 

Bearings 

The bearings used in the progressive and 
selective type transmissions may be either the 
plain roller bearing, the tapered roller bearing, 
or the annular ball bearing of either the single 
or double row construction. Some transmis¬ 
sions are equipped with plain bronze or babbitt 
bearings. 

Progressive Type 

In the progressive type of transmission as 
shown in Fig. 113, the clutch shaft fits in a 
bearing mounted in the transmission housing. 
On the end of the clutch shaft, inside the 
transmission housing, is fastened the clutch 
gear, and meshing with this gear is another 
gear usually of larger diameter, called the 
countershaft drive gear, since it is mounted on 
a countershaft placed at one side of or below" 



TRANSMISSIONS 


155 


the clutch shaft. These two gears are called 
the constant mesh gears, being engaged at all 
times and providing a positive continuous drive 
for the countershaft. The countershaft runs 
in bearings mounted in the transmission hous¬ 
ing and has three other gears rigidly mounted 
upon it, either keyed or shrunk on, or ma¬ 
chined integral with the shaft. They are 
called the intermediate or second speed gear, 
the low speed gear and reverse gear. 

The main shaft or transmission shaft runs 
in a bronze, roller, or circular ball bearing in 
the end of the clutch shaft and another in 
the opposite end of the transmission housing. 
On this shaft which is squared or splined, are 
two sliding gears, fastened together. They are 
moved back and forth on the shaft by a shift¬ 


ing fork, operated from outside the housing 
by a shifting lever. These gears engage with 
the countershaft gears to obtain different 
speeds. 

When the larger sliding gear on the trans¬ 
mission shaft engages with the small low speed 
gear on the countershaft, there are two re¬ 
ductions, the first through the constant mesh 
gears and the second through the low speed 
gears. 

To slide these gears into mesh, it is neces¬ 
sary to disengage the power connection be¬ 
tween the engine and the transmission. This is 
accomplished by disengaging the clutch. As 
both sliding members are connected together, 
it is necessary to have only one shifting collar, 
one shifting fork and one shifting bar. Re- 



PROGRESSIVE TYPE TRANSMISSION, 



3-SPEED FORWARD, 

1 

REVERSE 

A. 

Clutchshaft. 

N. 

First speed notch. 

B. 

Clutch gear. 

0. 

Reverse notch. 

C. 

Third speed driving dogs. 

P. 

Low and reverse sliding gear. 

D. 

Second and third speed sliding gear. 

Q. 

Transmission shaft. 

E. 

Shifting fork. 

R. 

Reverse idler gear. 

F. 

Shifting collar. 

S. 

Reverse countershaft gear. 

G. 

Gear shift bar. 

T. 

Low speed countershaft gear. 

H. 

Gear shift lever. 

U. 

Countershaft. 

I. 

Quadrant. 

V. 

Second speed countershaft gear. 

J. 

Pawl. 

W. 

Countershaft drive gear. 

K. 

Third speed notch. 

X. 

Bearing bushings. 

L. 

Second speed notch. 

Y. 

Transmission case. 

M. 

Neutral notch. 


























































































































































156 


CHASSIS 


! 



SINGLE SPRING, DRY DISC CLUTCH AND SELECTIVE TRANSMISSION, 
THREE SPEED FORWARD, ONE REVERSE 


A. Crankshaft. 

B. Flywheel. 

C. Driving studs. 

D. Driven studs. 

E. Pressure plate. 

F. Clutch release fork. 

G. Gear lock. 

H. Shifting forks. 

I. High speed sliding gear. 

J. High speed internal gear. 

K. Low and reverse sliding gear. 

In this construction the transmission gears are not 
mounted conventionally, which results in the gear shift 
not being standard. That is, by moving the shifting 
lever forward, low and high are obtained—instead of 
reverse and second, as in the standard transmission. 
With this mounting of the gears, when the high speed 
sliding gear (I) is meshed with the high speed internal 
gear (J), the countershaft is disconnected. When driv¬ 
ing in high speed, the power is transmitted from sliding 
gear (I), through (J) to shaft (N). The countershaft 
remains stationary. When the sliding gear (I) is 


L. Shifting collars. 

M. Second speed sliding gear. 

N. Main shaft or transmission shaft. 

O. Universal joint. 

P. Slip joint. 

Q. Countershaft. 

R. Countershaft second speed gear. 

S. Countershaft low speed gear. 

T. Countershaft reverse gear. 

U. Countershaft drive gear. 

V. Countershaft bearings. 

moved out of mesh with (J), it engages with the coun¬ 
tershaft drive gear (U), transmitting the power through 
the countershaft for the other speeds. 

This construction employs three sliding gears instead 
of two (the usual number for a three speed forward 
transmission). One sliding gear (I) moves back and 
forth on the square clutch shaft. The other two (K) 
and (M) move back and forth on the splined shaft (N). 
The gears (I) and (M) are controlled by the same 
shifting bar. 























































































































































































TRANSMISSIONS 


157 


verse is obtained by sliding the large sliding 
gear into mesh with the reverse idler. The 
reverse gear on the countershaft is usually 
smaller than the low speed gear, which allows 
the countershaft gear to slide in line, but not 
in mesh with it. By interposing an idler gear 
between the main transmission shaft and the 
countershaft, it reverses the direction of rota¬ 
tion of the transmission shaft. 

To shift from reverse to neutral, it is neces¬ 
sary to pass the large sliding gear through the 
low speed gear, causing a grating noise, which 
is a disadvantage of this type of transmission. 

To start the car, disengage the clutch and 
move the gear shift lever until the low speed 
sliding gear meshes with the low speed counter 
shaft gear, then allow the clutch to gradually 
engage. 

To shift the gears into second speed, dis¬ 
engage the clutch again, slide the second speed 
gears into mesh and then engage the clutch. 
The second speed sliding gear engages with 
the second speed countershaft gear, which is 
larger than the low speed countershaft gear, 
giving a higher speed but still a reduction to 
the drive. 

To obtain third speed, there are dogs ma¬ 
chined on one end of the sliding gear to engage 
with the dogs machined on the end of the 
clutch gear. This gives a direct drive through 
the main drive shaft without taking any driv¬ 
ing strains through the countershaft. 

Sometimes, when shifting gears, the teeth on 
the gears, are in such a position that they can¬ 
not slide into mesh; that is, the teeth in one 
gear will line up with the teeth in the other. 
This makes it impossible to slide the gears 
into mesh, until the clutch is engaged the least 
bit to turn 'the countershaft over to a new 
position so that the teeth can mesh properly. 
The teeth on these grears are generally 
rounded or chamfered to make shifting easier. 

The gears are made of alloy steel, heat 
treated and hardened to reduce wear and make 
them tough. If the teeth are brittle, the ends 
will break when sliding them into mesh. This 
is one of the most common transmission 
troubles. 

The bearing mountings on either end have 
felt washers to prevent the grease from leak¬ 
ing through. The transmission is partly filled 
with an oil, called 600-W (steam cylinder oil), 
or light cup grease. This heavy oil has a ten¬ 
dency to cling to the surfaces of the teeth bet¬ 
ter than other oils. Some oil, although just as 
heavy as 600-W, will not have the same ten¬ 
dency to cling to the gears. The correct 
amount of oil to put into the transmission 
housing is just enough for the gears to 


run in, never up to the center of the shaft. 
If the teeth of the gears are running in 
the oil, they will carry the oil upward, lubri¬ 
cating all bearings and the upper gears. 

This transmission has only one sliding mem¬ 
ber and one shifting bar; therefore, the gear 
shift lever that is used to shift the gears will 
have only a backward and forward motion. 
The end of the transmission in which the con¬ 
stant meshed gears are placed, and the shift¬ 
ing lever connection determines whether the 
reverse position of the shifting lever is forward 
or backward. First speed will be adjacent to 
the reverse position, with neutral, second and 
third following in order. 

The progressive transmission may be made 
in the four speed type, in which case there 
is one extra forward speed. If this trans¬ 
mission is used in a truck, the fourth speed will 
be engine speed, the others being reduced, 
thus employing a higher engine speed to get 
the truck under motion and to pull a heavy 
load. If the four speed progressive type trans¬ 
mission is used on a touring car or a racing 
car model, the fourth speed will be an increase 
over the engine speed, the third speed being a 
direct drive. 

Selective Type 

The construction of the selective type trans¬ 
mission does not differ greatly from the pro¬ 
gressive, except that the sliding member is 
divided into two parts. The sliding gear with 
which low and reverse speeds are obtained is 
separate from the second and third speed slid¬ 
ing gear. Each sliding member has a separate 
shifting fork and shifting bar to which a single 
shifting lever connects. This changes the gear 
shift considerably from that which is employed 
on the progressive type. On the selective type 
gear shift the lever is shifted over to either side 
and then forward or backward. On one side, 
depending entirely upon how the gear shift 
bars are arranged, are low and reverse. On the 
other side are second and high. Reverse and 
second are either both backward or both for¬ 
ward, and first and high are opposite to these 
respectively. 

The gear shift lever which is operated by the 
driver may operate in a gear shift gate, made 
in the form of an H which is called an “H” 
plate. When the “H” plate is used, the lower 
end of the shifting ^lever below the fulcrum 
moves in the same direction as the upper end, 
when sliding it sideways. To shift from one 
side to the other causes the shifting lever 
to slide along on the shaft, but for the for¬ 
ward and backward movement of the gear 
shift lever, the lower and upper ends move in 
opposite directions. (Continued on Page 161) 




158 


CHASSIS 



MM; 




pTI 

ti 


IQ[| 

n 


1 j 

L±L 

■pM 


FIG. 115 












































































































































































































































































































TRANSMISSIONS 


159 


FIG. 115 


MULTIPLE SPRING, DRY DISC CLUTCH, SELECTIVE 
TRANSMISSION, 3-SPEED FORWARD 
AND ONE REVERSE 


A. 

Crankshaft. 

U. 

Second and high speed sliding gear. 

B. 

Flywheel flange. 

V. 

Transmission shaft pilot bushing. 

C. 

Flywheel bolt. 

W. 

Gear shift lever. 

D. 

Flywheel. 

X. 

Ball and socket bearing. 

E. 

Clutch shaft bearing. 

Y. 

Shifting collars. 

F. 

Driven disc facing. 

Z. 

Shifting forks. 

G. 

Driving disc. 

1. 

Low and reverse sliding gear. 

H. 

Clutch pressure plate. 

2. 

Transmission shaft. 

I. 

Clutch spring retainer. 

3. 

Transmission shaft rear bearing. 

J. 

Clutch spring. 

4. 

Bearing lock. 

K. 

Clutch housing. 

5. 

Felt washer. 

L. 

Inspection plate. 

6. 

Countershaft reverse gear. 

M. 

Felt washer. 

7. 

Countershaft low-speed gear. 

N. 

Driven disc. 

8. 

Countershaft second-speed gear. 

0. 

Clutch release collar, thrust bearing and adjusting 

9. 

Countershaft drive gear. 


nut. 

10. 

Transmission housing. 

P. 

Gear shifting bar. 

11. 

Drain plug. 

Q. 

Gear lock. 

12. 

Countershaft bearing bushing. 

R. 

Clutch shaft. 

13. 

Countershaft nut. 

S. 

Clutch gear. 

14. 

Oil hole. 

T. 

Clutch shaft bearing. 




Disassembling the Clutch and Transmission 


Remove the inspection plate (L) 
from the clutch housing, the spring 
retainers (I), the bolts holding the 
clutch housing on to the crankcase, 
and slide the housing away from 
the flywheel. 

To disassemble the transmission, 
remove the bolts holding the shift¬ 
ing lever mounting on the trans¬ 
mission housing. Lift this assem¬ 
bly up, then remove the headless 
set screws that hold the shifting 


rods in the case. The shifting rods 
can now be removed. Remove the 
bolts holding the bearing retainers 
in the case, also remove the re¬ 
tainers and bearings, pull the 
transmission shaft out of the slid¬ 
ing gears and transmission case, 
remove the clutch gear, lift the 
sliding gears out of the case, then 
remove the cotter pin and castle 
nut from the countershaft, and 
also remove the countershaft. Now 


lift the countershaft gears from 
the housing. 

The bronze bearings in the coun¬ 
tershaft gears can be replaced with 
new ones and then reamed to fit the 
countershaft. These bearings are 
lubricated by the oil that passes 
through the oil hole (14). 600-W 

oil is the proper lubricant to use. 
Do not have the oil level above the 
countershaft, as the gears on the 
countershaft will carry the oil on 
to the other gears and bearings. 




S.A.E. 

STANDARD. 



FIG. 116 



POSSIBLE GEAR SHIFTS AND LEVERS 









































































































160 


CHASSIS 



FIG. 117 




















































































































































































































































































































































































































TRANSMISSIONS 


161 


FIG. 117 


TRANSMISSION ASSEMBLY EMPLOYED WITH 
FOUR WHEEL DRIVE 


Gear lock. 

Shifting bars. 

Shifting forks. 

Transmission shaft. 

High speed sliding gear. 

Third speed sliding gear. 

Second speed sliding gear. 

Low speed sliding gear. 

Reverse speed sliding gear. 

Reverse speed sliding gear. 
Countershaft low and reverse gears. 
Countershaft second speed gear. 


M. Countershaft third speed gear. 

N. Countershaft high speed gear. 

O. Differential case. 

P. Differential drive gear. 

Q. Front wheel driving shaft. 

R. Rear wheel driving shaft. 

S. Radial bearing. 

T. Thrust bearing. 

U. Felt oil retaining washer. 

V. Retainer collar. 

W. Countershaft. 


A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

' 1 . 

J. 

K. 

L. 

In the types of trucks in which 
the power is applied to all four 
wheels, a special form of gear set 
is necessary, in which the main 
drive will be directed to a cross 
shaft, which in turn will distribute 
power to both front and rear axles. 
In the illustration on opposite page, 
a standard American design four 
speed gear set for four wheel drive 
is shown. 

The engine pow'er is delivered to 
the shaft (D). This main shaft 
carries two sets of sliding gear 
members. Engaging (H) and (K) 
gives low speed; (G) and (L), 
second speed; (F) and (M), third 
speed and (E) and (N), high 
speed. Reverse speed is obtained 
by meshing (J) with (G) and (I) 
with (K). 

It will be observed that there is 


no direct drive on high or fourth 
speed, in the sense of having no 
gears transmitting power, as is the 
case in most passenger car trans¬ 
missions. 

The drive on the three lowest 
forward gears is through four 
gears; that on the main shaft turn¬ 
ing the corresponding member on 
the countershaft in the reverse di¬ 
rection to engine rotation. 

The high speed gear (N) imparts 
its power to the large spur gear 
(P) carried by the differential cas¬ 
ing (0). This results in the driv¬ 
ing shafts (R) and (Q) turning in 
the same direction as the crank¬ 
shaft. On high speed, only three 
gears are used for power transmis¬ 
sion. On reverse speed the power 
is transmitted through six gears. 

The bearing mounting on the 


main drive shaft from the engine 
is clearly shown, as are also the 
method of using single row annular 
bearings (S) on the countershaft 
with special thrust members (T) 
and the double row mounting of the 
differential case (0). 

It will be observed that stuffing 
boxes are provided on the outside 
of the lower shaft bearing housings. 
This is necessary because this shaft 
is mounted lower than the other 
two and is covered by lubricating 
oil, which would be apt to leak 
through the closure members if no 
means were provided for its posi¬ 
tive retention. Note that all bear¬ 
ings are mounted in removable 
housing members instead of seating 
.directly in the transmission case 
casting. 


The shifting bars, which are located in the 
transmission housing, have recesses cut in 
them in which the gear shift lever engages. 
These bars are arranged so that when in the 
neutral position, the lever cannot be shifted 
backward and forward. On the majority of 
modern transmissions, a ball and socket shift¬ 
ing lever is employed. On this type, when the 
shifting lever at the top is moved sideways, the 
bottom moves in the opposite direction. This 
type of lever also necessitates a device to pre¬ 
vent the sliding of both shifting bars at the 
same time. This is known as the inter-locking 
device. 

INTERLOCKING DEVICE AND GEAR LOCK 
ASSEMBLY 

The purpose of the interlocking device is 
to prevent the shifting of two sets of gears 
into mesh at the same time. It consists of 
either a dog or ball mounted in the transmis¬ 
sion case between the shifting bars. Besides 
the interlocking device mentioned above, the 
shifting bars are provided with “V” shaped 
notches, in which a small dog engages, the dog 
being held in place by a spring. This dog pre¬ 
vents the gears from sliding back and forth. 


for when the gears are properly meshed for 
any speed, or in neutral, one of the notches 
lines up with the dog; but when attempt¬ 
ing to shift the gears, this notch and spring 
tension are not noticeable to the driver, due to 
the leverage of the gear shift lever. This is 
termed the gear lock. 

The notches and dogs will wear in time, al¬ 
lowing the gears to come out of mesh. To 
remedy this, file the notches deeper and grind 
the dog to the proper shape. Sometimes 
the shifting forks and lever become sprung or 
out of alignment, which prevents the sliding 
gear from meshing properly and the locking 
notch in the shifting bar from lining up with 
the dog. This can be checked by placing 
the shifting lever in position and removing the 
adjusting nut, spring and dog of the gear lock. 
The trouble may be caused by a lack of spring 
tension which can be increased by tightening 
the adjusting nut. 

The gear lock sometimes becomes worn, al¬ 
lowing the dog to turn over in the notch and 
perhaps locking the shifting bars so they can¬ 
not be shifted. When this occurs, file the notch 
in the shifting bar deeper and ream the hole 
larger. Tap new threads in the hole and re- 




162 


CHASSIS 



FIG. 118 


SELECTIVE TRANSMISSION—FOUR SPEED FORWARD 


A. 

Clutch shaft. 

G. 

Fourth speed sliding gear. 

M. 

Countershaft. 

B. 

Clutch gear.- 

H. 

Transmission shaft. 

N. 

Countershaft drive gear. 

C. 

Third speed clutch gear (internal). 

I. 

Fourth speed countershaft gear. 

0. 

Countershaft bearing. 

D. 

Third speed sliding gear. 

. 1 . 

Reverse countershaft gear. 

P. 

End play adjusting nut. 

E. 

Second speed sliding gear. 

K. 

First speed countershaft gear 

Q. 

Shifting bars. 

F. 

First and reverse sliding gear. 

L. 

Second speed countershaft gear. 

R. 

Reverse idler gear. 


In this construction, (D) meshed with (C) gives the 
third speed drive direct from clutch shaft (A) to trans¬ 
mission shaft (H). The sliding gear (E) meshed with 
(L) gives the second speed drive through the counter¬ 
shaft. Low speed is obtained by meshing the sliding 
gear (F) with (K). Reverse speed is obtained by mesh¬ 
ing (F) with the reverse idler (R), which is always in 


mesh with the countershaft gear (J). Engaging the 
sliding gear (G) with the countershah gear (I) gives 
the fourth speed drive, which steps up the speed of 
the mainshaft, driving it at greater than engine 
speed. The radial load of the shafts is taken by annu- ' 
lar bearings. The alignment and end play adjustment 
of the countershaft is made through the plug (P). 

























































































































































































































































































































































































































TRANSMISSIONS 


163 


place with a new oversize dog, spring and nut. 
The interlocking device wears very little, but 
should it become worn, it may be repaired by 
filing the notches deeper with a rat tail file and 
replacing with oversize balls. 

On the propeller shaft end of the transmis¬ 
sion, the shaft is either splined or squared to 
accommodate a universal joint which con¬ 
nects the propeller shaft and transmission 
shaft. 

Planetary Type Transmission 

The Ford transmission is a typical planetary 
type transmission. It has a low and high speed 
forward and one speed reverse. The flywheel 
and tail shaft are bolted to the end of 
the crankshaft. The flywheel has three pins 
pressed into it, which are spaced 120° apart. 
The triple gears are mounted and revolve on 
these pins. These gears are fastened to¬ 
gether, either made solid or riveted, and have a 
bronze bushing pressed on the inside for a 
bearing. The gears mounted nearest the 


flywheel have twenty-seven teeth, those in 
the middle have thirty-three teeth, and the 
others have twenty-four teeth. These gears 
revolve as a single unit on their axes, which 
are the pins that are pressed into the flywheel. 

There are three drums in this clutch and 
transmission. The drum nearest the fly¬ 
wheel is the reverse drum. This drum has 
a hub on the end of it on which is cut a gear 
containing thirty teeth which is in constant 
mesh with the twenty-four tooth gears of the 
triple gear set. On the interior of this re¬ 
verse drum hub is a bronze bushing to accom¬ 
modate the hub of the drum next to it, which 
is the low speed drum. The hub of the low 
speed drum revolves inside the hub of the re¬ 
verse drum. The low speed drum has an ex¬ 
tension that continues through the reverse 
drum, on which is cut another gear contain¬ 
ing twenty-one teeth, and this gear is in con¬ 
stant mesh with the^ thirty-three tooth gears 
of the triple gear set. In the interior of this 
low speed drum there is another bronze bush- 



FIG. 119 


GEAR LOCK AND INTERLOCKING DEVICE 
ASSEMBLY 


A. 

Transmission case. 

E. 

Shifting bars. 

B. 

Gear lock. 

F. 

Gear lock spring. 

C. 

Shifting bar locking notch. 

G. 

Gear lock spring nut. 

D. 

Interlocking device. 

H. 

Gear lock dog. 























































164 


CHASSIS 




FJG. 120 



































































































































































































































































































TRANSMISSIONS 


165 


A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

J. 

DISASSEMBLING THE FORD 
TRANSMISSION AND 
CLUTCH 

Remove the universal joint, then 
remove the driving plate (N) hy 
removing the screws (Q). The set 
screw (S) should next be removed, 
after which the clutch disc drum 
(2) should be drawn off endwise. 

Next remove the Woodruff key 
(K) from the transmission shaft. 
The transmission can now be re¬ 
moved from the shaft by turning 


FIG. 120 

FORD PLANETARY TRANSMISSION 

JJ. Reverse gear (30 teeth). 

K. Woodruff key. 

L. Slow speed drum. 

M. Driving disc. 

N. Driving plate. 

O. Clutch finger. 

P. Clutch finger adjusting screw. 

Q. Driving plate screw'. 

R. Reverse drum. 

S. Clutch disc drum set screw. 

T. Triple gear. 

it as it is being withdraw'n. 

To separate the drums, the driven 
27-tooth gear (I) should be pressed 
off the brake drum hub and the 
keys should be removed. 

Repairs 

The triple gear shafts (B) can 
be pressed out of the flywheel. The 
bronze bearings in the triple gear 
sets are also removable, should it 
be necessary to replace them when 
worn. The bronze bearings in the 
low'-speed, reverse and brake drums 


U. Push ring pin. 

V. Clutch shift. 

W. Clutch spring. 

X. Clutch spring thrust ring pin. 

Y. Clutch spring support. 

Z. Universal joint. 

2. Clutch disc drum. 

3. Clutch push ring. 

24. 24 tooth gear. 

27. 27 tooth gear. 

33. 33 tooth gear. 

are also removable by being pressed 
out of the drum hubs. 

It is behind the bearing flange 
(H) that the spacing shims are 
placed to remove the end play from 
the clutch. The bronze bearing in 
the driving plate hub that bears 
on the transmission shaft can be 
replaced. The new bearings, after 
being pressed into place, must be 
reamed a snug fit to fit their re¬ 
spective shafts. An expansion 
reamer should be used when ream¬ 
ing these bearings. 


Transmission gear shaft or tail shaft. 
Triple gear shaft. 

Crankshaft. 

Brake drum. 

Driven disc. 

Flywheel. 

Flywheel bolt. 

Driven gear sleeve bushing (end 
thrust bearing). 

Driven gear (27 teeth). 

Slow speed gear (21 teeth). 


ing in which the hub of the third drum re¬ 
volves. This is the brake drum hub, on the 
end of which is keyed a separate gear with 
twenty-seven teeth which engages with the 
twenty-seven tooth gears of the triple gear 
set. The brake drum has six internal splines 
on which the high speed driven discs are 
mounted. On the end of this drum is a plate 
that is bolted on with six cap screws. This 
plate has a hub, in the rear end of which is a 
square hole to accommodate one end of the 
universal joint. 

The clutch disc drum is mounted on the 
end of the tail shaft and revolves as a unit 
with it. This drum is made rigid with the 
tail shaft by means of a woodruff key and 
a set screw. The woodruff key ^ is to pre¬ 
vent the drum from turning on the tail shaft, 
and the set screw is to prevent end play. The 
drum is mounted in such a position that it 
comes on the interior of the brake drum. The 
clutch disc drum has six keyways cut in the 
outer circumference to accommodate the driv¬ 
ing discs, which are the small ones. 

The larger discs, which are the driven discs, 
slip freely over the clutch disc drum. They 
engage with the six splines on the interior of 
the brake drum. The driving plate is provided 
with three fingers spaced 120° apart, which 
bear on the clutch push ring that is placed 
against the discs. When the fingers on the 
driving plate are pushed forward by the clutch 
spring, the discs are forced together, giving a 
direct drive. 


For the low and reverse speeds, the drive 
is obtained through the triple gears, through 
the hub of the brake drum and the driving 
plate, to the universal joint and propeller 
shaft. 

For high speed the drive is through the tail 
shaft which is bolted to the crankshaft, the 
clutch disc drum, driving and driven discs, 
brake drum and driving plate, to the universal 
joint and propeller shaft. 

The three drums which are the reverse, low 
speed and brake respectively, have contrac¬ 
ting bands around them. These contracting 
bands are provided with linings which are riv-- 
eted on in a manner similar to ordinary brake 
linings. There are three foot pedals for this 
transmission and clutch. The one at the driv¬ 
er’s left is the low and high speed clutch pedal, 
the center one is the reverse pedal, and the 
one on the right is the brake pedal. The low 
and reverse speeds are obtained by pushing 
forward on their respective foot pedals. By 
pushing forward on the foot pedals, the bands 
are contracted around the drums, thus holding 
them stationary. 

Operation 

Low: Pushing forward on the low speed 
pedal holds the low speed drum stationary. 
Holding this low speed drum stationary 
also holds the twenty-one tooth gear on 
the hub of the low speed drum stationary, 
as it is rigid with the drum. When the 
flywheel revolves, it carries the triple gears 




166 


CHASSIS 


around with it. This causes the thirty- 
three tooth gear to roll around the outside of 
the twenty-one tooth gear, which at this time 
is stationary. In one revolution of the fly¬ 
wheel, the thirty-three tooth gear will not 
make one complete revolution on its own 
axis, (which is the pin pressed into the fly¬ 
wheel), but makes only 21/33 of a revolution. 
The three triple gears also turn 21/33 of a 
revolution, as all three of them revolve as a 
unit. As the forward gear of this triple gear 
set has twenty-seven teeth and is in mesh with 
the twenty-seven tooth gear which is rigid with 
the hub of the brake or driving drum, it im¬ 
parts motion to this drum. The triple gear 



(Solid arrow on 27 tooth sun gear shows direction of 
rotation, direct drive, forward. Dotted arrow, direction 
of rotation in reverse gear.) 


sets roll around on the twenty-seven tooth 
gear, but turn less than one revolution 
while the flywheel is turning one complete 
revolution, therefore, it drags the twenty- 
seven tooth gear on the forward end of the 
brake drum ahead with it, just as much as the 
triple gears are losing on their axes during each 
revolution of the flywheel, which is 12/33 of 
a revolution. If the driving drum is dragged 
ahead 12/33 of a revolution during each revo¬ 
lution of the fl)Dvheel, it will require as many 
revolutions of the flywheel to make one revo¬ 
lution of the brake drum as 12 is contained 
in 33, which is 2%. It requires 2% turns 
of the flywheel to drag or drive the brake drum 
ahead one complete revolution. 

Reverse: To obtain the reverse speed, it is 
necessary to push forward on the center foot 
pedal, which causes the reverse drum to be held 
stationary. When this drum is held stationary, 
the thirty-tooth gear is also held station¬ 
ary. With the flywheel revolving and the twen¬ 
ty-four tooth gear in mesh with the thirty- 
tooth gear, the triple gears turn ly^ revo¬ 
lution on their own axes while the flywheel 
turns one revolution. This is due to the fact 
that while the flywheel is revolving, the twen¬ 


ty-four tooth gear is rolling around on the out¬ 
side of the thirty tooth gear. In one revolu¬ 
tion of the flywheel, the twenty-four tooth 
gear travels through thirty teeth or turns l^/t 
revolutions; hence, the complete set of triple 
gears turns li/4 revolutions, ly, revolutions of 
the twenty-seven tooth gear of the triple gears 
causes the driven gear (which is rigid with the 
brake drum) to be driven in the opposite or 
the reverse direction % of a revolution while 
the flywheel revolves once. Therefore, in re¬ 
verse it requires as many revolutions of the 
flywheel to turn the brake drum one revolution 
as 6 is contained in 24, or 4 revolutions of the 
flywheel to one revolution of the brake drum. 

Adjustments 

The adjustments for the reverse and low 
speeds are made on the bands, while the ad¬ 
justments for high speed are made by means of 
the three Angers which press against the push 
ring. The pressure of the spring against all 
three fingers should be the same. The small 
screws in the fingers are the adjusters. When 
the low speed band is contracted, the clutch 
shifting collar is moved backward. There are 
two adjustments in this connection. One is the 
connecting link at the lower end of the pedal. 
This adjustment is to change the position of 
the low speed or clutch pedal. The other is 
the screw which rides on the hand brake lever 
cam, which serves to disengage the clutch 
when the brake lever is pulled halfway or all 
the way back. 

There are three positions of the emergency 
brake lever. When this brake lever is in its 
extreme forward position and the foot pedal 
is all the way back, it allows the clutch spring 
to engage the discs for high speed. With the 
hand brake lever half way back the low speed 
may be engaged but not high speed, due to the 
fact that on pulling the brake lever backward, 
it moves the cam back, thus disengaging the 
clutch. If the hand lever is drawn all the way 
back, the high speed clutch is held in neutral, 
and at the same time the emergency brake is 
engaged. The low speed band can still be con¬ 
tracted, but the engine will be stalled, because 
the emergency brake is engaged and the high 
speed clutch disengaged. The radial and 
thrust bearings employed in this transmission 
are constructed of bronze and are not ad¬ 
justable. 

Repairs 

When excessive wear is evidenced by lost 
motion, the transmission should be disassem¬ 
bled and the worn bushings pressed out. The 
new bushings, after they are pressed in, should 
be reamed to an easy rolling fit, always remem¬ 
bering that a certain amount of clearance must 
be allowed for a film of oil. These bearings are 



TRANSMISSIONS 


167 


provided with spiral oil grooves, so that the 
revolving of the drums causes the oil to be 
distributed to the bearing surfaces. 

The bushing on the interior of the brake 
drum hub has a shoulder on the outside which 
revolves with the brake drum. This shoulder 
is the end thrust bearing. When the shoulder 
wears, it allows the brake drum hub to slip 
back and forth on the tail shaft between the 
flywheel and the clutch drum. To remedy this 
(if the bushing is not worn more than one- 
third), cut the oil grooves deeper and place 
shims between the shoulder and brake drum. 
If the shoulder is worn more than one-third. 


replace it with a new bushing. This replace¬ 
ment is to overcome end play. 

Care must be taken that the bands and lin¬ 
ings are in good condition. If the rivets are ex¬ 
posed or the linings worn, it may result in scor¬ 
ing and roughening the surface of the drums. 
After the drums are scored, it is impossible to 
prevent excessive wear of the linings. 

The brake band contracting around the ex¬ 
terior of the brake drum stops the car, because 
the driving plate which is bolted to the brake 
drum connects with the universal joint and 
propeller shaft, which in turn forms the con¬ 
nection with the rear axle and wheels. 



CONTROLS OF THE FORD PLANETARY 
TRANSMISSION 


A. 

Hand brake lever. 

J. 

Low speed adjusting screw. 

B. 

Brake foot pedal. 

K. 

Lowspeed adjusting screw lock nut. 

C. 

Clutch and low speed foot pedal. 

L. 

Reverse adjusting nut. 

D. 

Low speed connection clevis. 

M. 

Transmission band springs. 

E. 

Clevis lock nut. 

N. 

Clutch release fork. 

F. 

Clutch lever cam screw. 

0. 

Clutch spring. 

G. 

Clutch release cam. 

P. 

Clutch finger adjusting screw. 

H. 

Brake band. 

Q. 

Clutch finger. 

I. 

Brake adjusting nut. 

R. 

Reverse foot pedal. 


The low speed adjustment of the drum is made by 
loosening the lock nut (K) and adjusting the band with 
the adjusting screw (J). The reverse adjustment is the 
nut (L). The brake adjustment is the nut (I). The 
clevis (D) with the lock nut (E) is the adjustment for 


the position of the low speed pedal. The clutch adjust¬ 
ment for neutral, when the hand lever is in neutral 
notch, is the screw (F) and lock nut. The adjustments 
for the clutch, if it slips while driving in high, are the 
three adjusting screws (P) in the fingers. 















168 


CHASSIS 


UNIVERSAL AND SLIP JOINTS 

The purpose of the universal joint is to con¬ 
nect two revolving shafts or rods whose axes 
are at different angles, and permit a change in 
the angle of the axes while they are turning. 
The universal joint, as applied to the automo¬ 
bile, connects the propeller shaft with the 
transmission and in some cases with the rear 
axle. 

The rear axle bounds up and down in a line 
which is not a true radius from the point at 
which the universal joint connects to the trans¬ 
mission. This necessitates a construction 
which will allow for end movement of the 


propeller shaft in ’ the universal joint. To 
compensate for the variable distance between 
the transmission and rear axle caused by this 
up and down movement of the axle, the uni¬ 
versal joint hub and the propeller shaft connec¬ 
tion are usually square or splined, which allows 
the propeller shaft to slip back and forth in 
the joint. This is called a slip joint. 

The universal joint is constructed by using 
two two-pronged forks straddling a center 
block or spider in such a manner that the axes 
of the fork trunnions are at right angles to 
each other, thus permitting flexing in four 
directions. 



FIG. 123 


FLEXIBLE COUPLING AND UNIVERSAL JOINT 



No. 1 


No. 2 


A. 

Spider. 

P. 

Transmission shaft, universal joint flange. 

V. 

B. 

Fabric. 

Q. 

Propeller shaft. 

W. 

C. 

Washers. 

R. 

Universal joint casing nut. 

X. 

D. 

Propeller shaft. 

S. 

Adjusting nut. 

Y. 

E. 

Transmission shaft. 

T. 

Outer casing. 

Z. 

F. 

Key. 

U. 

Universal joint centre cross (or spider). 


G. 

Castle nut. 




Packing. 

Inner casing. 

Universal joint flange yoke. 
Filling hole. 

Universal joint slip yoke. 











































































































































DIFFERENTIAL 


169 


Due to the peculiar action of the universal 
joint when turning, the driven shaft that is 
connected to the universal joint does not re¬ 
volve at the same uniform speed but slows 
down and speeds up every half revolution. To 
overcome this, two joints are usually used. 

The universal joint is generally con¬ 
structed of heat treated alloy steel and is usu¬ 
ally enclosed in a housing which prevents the 
dirt and grit from working into the bearings. 
The housing should be packed with grease for 
lubrication. In some cases a leather boot is 
provided to enclose the universal joint and to 
hold the grease. 

FLEXIBLE COUPLINGS 

The flexible coupling or joint is used for 
the same purpose as the universal joint, but 
where the angle between the transmission 
shaft and the propeller shaft is not so great. 
The flexible coupling will not move to as great 
an angle as the universal joint. It is usually 
constructed of three principal parts, which are; 
two, three-pronged spiders fastened to either a 
steel disc or a fabric disc of some tough ma¬ 
terial made especially for this purpose. The 
prongs of the spiders are placed 60° apart, 
which allows the prong of each spider to come 
directly between two prongs of the other 
spider. 

The advantage of the flexible coupling over 
the universal joint is that it has less parts to 
wear, no bearings to replace, no lubrication 
needed and gives greater accessibility. 

PROPELLER SHAFTS 

The propeller shaft is employed in trans¬ 
mitting the power from the transmission shaft 
and universal joint to the pinion shaft and rear 
axle. The entire driving strain is transmitted 
through this propeller shaft, which necessitates 
a strong construction in which heat treated 
alloy steel is usually employed. The ends of 
the propeller shafts are generally squared or 
splined to allow the shaft to move back and 
forth in the universal joint as the axle bounds 
up and down. 

TORQUE MEMBERS 

The propeller shaft may be enclosed in a 
housing which is known as the torque tube. 
The purpose of this tube is to take the twist¬ 
ing strain that would come on the springs 
when the car is started, the clutch suddenly 
engaged, or a sudden acceleration of the en¬ 
gine. When the power is applied, the axle 
housing has a tendency to revolve in the 
opposite direction to the movement of the 
wheels. By fastening this torque tube to the 
axle housing' and' to a cross member at the 
universal joint, this torque strain is overcome 
but it still allows for the up and down move¬ 


ment of the rear axle. In some cases a torque 
arm is used instead of a tube. The torque 
arm fastens to the rear axle housing and 
is hinged to a cross shaft close to the uni¬ 
versal joint. When neither torque arms nor 
torque tube are provided, the torque strain is 
taken by the rear springs in which one extra 
heavy leaf is assembled. This is known as the 
Hotchkiss drive. 

THE DIFFERENTIAL ASSEMBLY 

The purpose of the differential is to allow one 
rear wheel to turn independent of, or faster 
than the other, which is necessary when mak¬ 
ing a turn. By studying the action of the 
rear wheels when the car is turning a corner, 
it is noted that the outside wheel travels a 
greater distance and at a greater speed than 
the inside wheel. In order to obtain maximum 
efficiency, it is necessary to drive both wheels, 
therefore, a differential has to be used in the 
rear axle assembly to provide for the higher 
speed of the outside wheel and still provide a 
drive on both wheels. 

The differential assembly is enclosed in the 
differential case to which the ring gear is 
riveted or bolted. The beveled drive pinion, 
which is keyed to the pinion shaft or propeller 
shaft, meshes with the beveled ring gear. The 
drive pinion is driven by the pinion shaft which 
is coupled to the propeller shaft either by a 
universal joint, or flexible coupling. 

Assembled in the differential case are the dif¬ 
ferential spider, the spider gears and the side 
gears. This spider may have either two, three 
or four prongs, on which are mounted the dif¬ 
ferential pinions or spider gears. The spider, 
is held rigidly between the two halves of the 
differential case and always revolves in the 
same direction and at the same speed as the 
ring gear. In mesh with the differential pinion 
gears are two side gears (beveled), which are 
sometimes called .the compensating gears. The 
side gears are mounted on the inner ends of 
the two halves of the rear axle shaft. The 
path of power from the propeller shaft to the 
axle shafts is through the driving pinion and 
ring gear to the spider, and from the spider 
gears through the side or compensating gears 
to the axle shafts. 

When driving straight ahead with the wheels 
turning at the same speeds, the spider gears 
do not turn on their axes but act as a lock be¬ 
tween the two side gears. When making a 
turn, the inside wheel and side gear offer more 
resistance than the outside wheel and side 
gear; hence, the inner side gear slows down 
or turns slower than the ring gear. The 
spider revolving faster than the inner side gear, 
causes the spider gears to revolve on the 



170 


CHASSIS 


spider, which drives the outer side gear faster 
than the spider and ring gear. The spider 
assembled in the differential case drags the 
spider gears ahead, and by revolving it around 
on the surface of the side gear that is turning 
slower, the other side of the spider gears are 
moved ahead faster than the spider and ring 
gear, thereby driving the outer side gear at a 
faster speed. 

For example, consider an ordinary automo¬ 
bile wheel. The point of the wheel that is in 
contact with the road is moving ahead at a 
slower speed than the very top of the wheel, 
due to the fact that the point of the wheel that 
is in contact with the road is like the fulcrum 
of a lever. Consider this wheel as a gear with 
another gear in mesh with it at the top. The 
point of the wheel that is in contact with the 
road corresponds to the point on the spider 
gear which is in mesh with the side gear 
that is either standing still, or moving at 
a slower speed; consequently, the gear that 
would be in mesh with the outside of that gear 


would travel faster. In like manner the 
side gear that is connected to the wheel 
shaft on the outside will, while making a turn, 
travel faster, due to being driven ahead by the 
action of the differential spider and pinion. 

It is necessary, if quietness of operation is 
desired, that the ring gear, w^hich is fastened 
to this differential case, should run exactly 
true. The loads that come on these beveled 
gears are uneven and it is difficult to keep 
them absolutely quiet. If a gear does not run 
exactly true, that is, if it is tight at one point 
and loose at another, it will cause the gears to 
“howl.” When riveting the ring gear on the 
differential case, the surfaces of both should 
be finished smooth and be free from dirt to 
insure a good contact. The rivets should, be 
draw’ll up w’hile still red hot. The advantage of 
having the rivets red hot is that when the steel 
is hot it is expanded. This causes the rivets to 
contract as they cool, resulting in a tighter fit. 

The axle shafts are fastened into the side 
gears in various manners. Some are fastened 



DIFFERENTIAL ASSEMBLY AND MOUNTING 


A. 

Left axle shaft. 

P. 

Differential case. 

B. 

Right axle shaft. 

G. 

Axle drive bevel gear (or ring gear). 

C. 

Differential pinion shaft. 

H. 

Axle housing. 

D. 

Differential pinion or spider gear. 

P. 

Axle drive bevel pinion (or pinion gear) 

E. 

Side gear (or compensating gear). 

R. 

Rivet. 

































































DIFFEREN TI AL —REAR AXLES 


171 


with a woodruff key and a horse shoe washer. 
The washer resting on the interior of the side 
gear, prevents the axle shaft from coming out. 
To remove the axle shaft from this essembly, 
it is necessary to separate the differential as¬ 
sembly and push the axle shaft inward, re¬ 
moving the horse shoe washer and then the 
woodruff key, which will allow the removal of 
the shaft. 

If the hole in the side gear is tapered another 
method of fastening is used. A fastening nut 
on the interior pulls the tapered axle shaft 
tightly into the side gear and the drive is 
through a woodruff key. In some axles the 
hole in the gear is either square or splined, in 
which case the axle shaft is not fastened in 
the side gear, but slides freely into the gear, 
being held in place by a retaining nut at the 
end of the axle. 

The type of axle housing usually determines 
the method of fastening the axle shafts in the 
gears. 

In many axles, the rear wheel hub is held 
to the axle shaft by a nut and the driving 
strain is taken by a key. The wheel is fast¬ 
ened to a tapered portion of the axle shaft. 
The axle shaft being tapered, allows the wheel 


to be held more tightly without depending en¬ 
tirely upon the key. The wheel should be 
pulled up as tightly as possible on the tapered 
portion of the shaft and the nut then locked 
with a cotter pin. On other types the axle shaft 
is not fastened rigidly in the wheel, the drive 
being obtained through a flange that is secured 
to the axle shaft. This type of fastening is 
used when the wheel is mounted on bearings 
on the exterior of the axle housing, and held on 
by a nut, in which case the axle shaft is used 
only to drive the wheel, and does not carry 
any of the weight of the car. 

REAR AXLES 

A dead axle has the road wheels mounted 
on a stationary member, these wheels being 
driven by chains. There is no provision in the 
axle itself for driving the wheels. 

A live axle is a general name for types of 
axles with revolving driving shafts mounted 
within the housing. 

Live axles are divided as follows: plain live, 
semi-floating, three-quarter floating and full 
floating. 

The type of axle is determined by the mount¬ 
ing of the bearings. 






Filling 
Plug 

Differential Gear 


FIG. 125 

SEMI-FLOATING AXLE, SHOWING BRAKE CONTROL 
AND SPRING MOUNTING 


Crease Retainer 


Keep Space 
Well Packed 
With Crease 


rrneei 

Grease 


Brake Retracting 
Springs 

Driving Pinion 
ng Nuts 

Spiral 

Bevel Driving 
Pinion 


Differential 











172 


CHASSIS 





SS 


7^^Z2& 


^tzzzza 






/ 







tH 

d 

»-H 


PLAIN LIVE AXLE 





































































































































































































REAR AXLES 


173 


In the plain live axle the axle 
shafts are held into the side gears 
by a key and washer. The key 
prevents the gears from turning on 
the axle shaft, and the washer pre¬ 
vents end movement of the axle 
shafts in the gears. 

On the outer end of the axle 
shaft, the wheel hub is keyed to the 
tapered portion of the shaft and 
held in place by a nut (B). To 
remove the end play in the drive 
shaft and pinion gear (0), place in 
an additional spacing shim (Q) or 
replace with a thicker one. To re- 


FIG. 126 

PLAIN LIVE AXLE 

move the end play in the differen¬ 
tial case (L), use a thicker thrust 
washer (J). The purpose of the 
felt washer (F) is to prevent the 
oil in the axle housing and differ¬ 
ential from working out on the 
brakes, which would cause a loss 
of oil as well as slipping brakes. 

To remove the axle shafts, jack 
up the car, disconnect the spring 
mounting, brake controls, universal 
joint, etc. Remove the axle, wheels, 
and drive shaft tube assembly 
from underneath the car. Remove 


hub cap (A) and nut (B), and with 
a wheel puller remove the wheel; 
take out the cap screws, remove the 
propeller shaft tube, and with it the 
drive shaft pinion gear (O) and 
bearings (P), (Q) and (R). Also 
remove bolts and separate the two 
parts of the axle housing. Remove 
the differential case bolts and force 
the two halves of the differential 
case apart. By moving the axle 
shaft inward far enough to remove 
the split washer (M), the axle shaft 
can be removed. 


Plain Live Type 

(Fig. 126) 

On a plain live axle, the inner and outer 
bearings are mounted on the axle shafts. The 
axle shafts fasten rigidly to the road wheels 
and differential side gears, and take all the 
strains, which are radial or weight, torque or 
driving and thrust or skidding. If an axle shaft 
breaks, the wheels will come off, necessitating 
the use of a truck or support of some kind 


being placed under the axle in order to tow the 
car to a garage. 

Semi-Floating Type 

(Fig. 129) 

On the semi-floating type axle, the outer bear¬ 
ings are mounted on the axle shaft the same as 
in the plain live, but the inner bearings are 
mounted on the differential housing or case 
instead of on the axle shafts. This relieves the 
axle shafts of the differential housing strain. 





Roller Bearings 
ral Bevel Driving Pinion 
al Spider 
iai Adjusting Nut 
er Roller Bearings 


FIG. 127 

SEMI-FLOATlNG AXLE 


Spiral Bevel Drive Gea 
Brake Shaft 
Brake Tube 
Oil Retainer 
Differential Taper Bearings 


Spring Pad 
Differential Pinion 
xle Bearing Retaining Nut 
Double Row Annular Axle Bearing.^ 
Outer Brake Band Anti-Rattle Spring 


Shaft 
Outer Brake 

I Gear 
Differential 




























174 


CHASSIS 


but the axle shafts still carry load, torque 
and thrust strains. On some axles of this 
type, the axle shafts are fastened into the 
differential side gears and the wheel is keyed 
on the shaft the same as in the plain live. In 
others the axle shafts are not fastened into 
the differential side gears, but are merely en¬ 
gaged, employing the use of a spline or square 
construction. On most semi-floating axles, 
the outer bearings are mounted on the tapered 
part of the shaft or against a shoulder on the 
shaft with a retaining and adjusting nut 
screwed inside the axle housing. This outer 
bearing takes the weight of the car and the 
skidding strains of the wheels, and with its 
mounting holds the axle shafts in place. 

Three-Quarter Floating Type 

(Fig. 130). 

In the three-quarter floating axle, the inner 
bearings are mounted on the differential hous¬ 
ing the same as in the semi-floating type. The 
bearings at the outer ends are mounted on the 
axle housing inside the wheel hub and are held 
on by a nut. The axle shafts take the torque 
and part of the thrust strains, and the wheels 
depend upon the axle shafts for alignment. 
The axle housing carries the radial load and 


part of the thrust strains. On some three- 
quarter floating axles, the shafts are fastened 
into the differential side gears, and the wheel 
is keyed on the axle shaft the same as in the 
semi-floating type. 

. Full Floating Type 

(Fig. 138) 

On the full floating type, the inner bearings 
are mounted on the differential housing the 
same as in the semi and three-quarter floating 
types. The outer bearings are mounted the 
same as in the three-quarter floating, except 
that each wheel has two bearings which are 
held on the axle housing by a retaining nut. 
The wheels do not depend on the shafts for 
alignment, and may be driven by a flange or 
jaw clutch which is fastened to the outer end 
of the axle shaft. The axle shafts catry only 
the torque strain. The axle housing carries 
the radial and thrust load. 

TYPES OF AXLE DRIVES 

The various types of live axles can be driven 
by a bevel gear, spiral bevel gear, worm gear, 
double reduction gear, or single chain. The 
dead type axle may be driven by double chains 
or internal gears. (Continued on Page 180) 


PINION BEARING 
ADJUSTING NUTv 


AXLE SHAFT 
BEARING 
ADJ. NUT 


AXLE SHAFT 
BEARING 




INION SPIDER 


PINION 

BEARINGS 


PINION 

DIFFERENTIAL BEVEL 
PINION 



DIFFERENTIAL BEARING 

DIFFERENTIAL BEVEL 
GEAR 

AXLE SHAFT 
'^|.THRUST BUTTON 


FIG. 128 

SEMI-FLOATING AXLE 














































































REAR AXLES 


175 







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Axle shaft. G. Differential bearing adjuster. 

Outer bearing. II. Differential thrust bearings. 

Axle shaft nut. I. Drive pinion shaft bearings. 

Differential case. J.. Axle drive bevel pinion adjuster. 

Axle shaft key. K. Hub cap. 


176 


CHASSIS 



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REAR AXLES 


177 






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FULL FLOATING AXLE EMPLOYING A DRIVING 
FLANGE TO TRANSMIT THE POWER FROM 
THE AXLE SHAFT TO THE WHEEL HUB 





































178 


CHASSIS 



SPIRAL BEVEL GEAR DRIVE REAR AXLE 











































































































































































































































REAR AXLES 


179 


FIG. 132 

SPIRAL BEVEL GEAR DRIVE REAR AXLE 


A. Axle drive pinion shaft. 

B. Axle drive bevel gear. 

C. Axle drive bevel pinion. 

D. Drive pinion adjusting sleeve 
lock. 

E. Front bearing adjuster lock. 

F. Front bearing adjuster. • 

G. Felt washer. 


H. Retainer. 

I. Drive pinion front bearing. 

J. Drive pinion rear bearing. 

K. Drive pinion adjusting sleeve. 

L. Rear bearing adjuster. 

M. Steel rivet. 

N. Differential spider gear pin. 

O. Differential case. 


P. Axle shaft. 

Q. Differential side gear. 

R. Differential spider gear. 

S. Differential adjuster lock, 

T. Differential adjuster. 

U. Differential bearing. 

V. Bevel gear housing cover. 

W. Lock retaining screw. 


The correct alignment of the pinion shaft is obtained 
by moving the adjusting sleeve (K), which is locked by 
the set screw (D). End play is taken up by tightening 
the adjuster (L). To remove the outer bearing .(I), 
remove retainer plate (H), adjuster lock (E) and ad¬ 
juster (F). 


The rear bearing (J) can be removed by unscrewing 
the lock screw (D), then the adjusting sleeve (K); after 
these are removed, pull the pinion gear off its shaft and 
^remove end play adjuster (L). The felt washer (G) 
acts as an oil retainer, preventing a loss of oil around 
the pinion shaft. The differential end play adjustment 
is made through the adjusters (T). 




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FIG. 133 

DIFFERENTIAL ASSEMBLY 



















180 


CHASSIS 


TYPES OF AXLE HOUSINGS 

Rear axle housings are usually divided into 
two general types: one piece, or bell type, and 
two or three piece, or divided type. 

There are two types of bevel gears used, the 
ordinary bevel gear with straight line teeth 
and the spiral tooth gear whose teeth curve 
around the gear cone in the shape of a spiral. 
The latter is more commonly used for passen¬ 
ger cars, the chief advantage being their noise¬ 
less operation at all speeds. 

Other advantages of the spiral bevel gear 
are; smaller number of teeth can be used per¬ 
mitting higher gear ratios; the form of the 
tooth is such that the point of contact is al¬ 
ways at the pitch line, or the point where there 
is no slipping between the teeth that are touch¬ 
ing, which makes a stronger tooth with prac¬ 
tically no wear and insures the quiet running; 
also more teeth in contact at one time giving 
added strength. 


REAR AXLE ADJUSTMENTS 

The clearance allowed between the teeth on 
new drive pinion and ring gears is about 
twelve-thousandths of an inch. When one new 
gear and one old gear are employed, as on a 
repair job, about eight-thousandths should be 
allowed. When both gears are old and “worn 
in” and are only being adjusted, a clearance of 
six-thousandths of an inch is usually sufficient. 
The above clearances may be obtained by the 
use of paper or a lead wire. When adjusting 
old gears take a tough piece of paper that 
measures three-thousandths of an inch. This 
paper, after passing between the gears, should 
show a good impression without being cut. A 
soft lead wire, when run through the gears and 
compressed, should measure the desired clear¬ 
ance. That is, the thickness of the wire or 
paper gives the clearance at the pitch line 
between the two gears. 

See that the gears do not bind at any point. 



FIG. 134 

TWO SPEED REAR AXLE 


A. 

Low speed axle drive pinion. 

G. 

High speed pinion gear 

B. 

Low speed axle drive bevel gear. 

H. 

Shifting bar. 

C. 

High speed axle drive hevel gear. 

J. 

Shifting fork. 

D. 

High speed axle drive pinion. 

K. 

Splined shaft. 

E. 

Shifting jaw clutch. 

L. 

Axle shaft. 

F. 

Low speed pinion gear drive. 




Greater reduction is obtained by sliding the shifting 
har (H) forward, which engages the teeth on the jaw 
clutch (E) with the teeth on the low speed pinion gear 
driving sleeve (F). The power is transmitted from the 
pinion gear (A) to the ring gear (B), through the differ¬ 


ential assembly to the axle shafts. 

If the shifting bar is moved back, the teeth on the jaw 
clutch (E) engage the teeth on the high speed pinion 
gear drive (G), transmitting the power from the pinion- 
gear (D) to the ring gear (C). 























































































































REAR AXLES 


181 


but have a free rolling contact all the way 
around. If too much clearance is allowed be¬ 
tween the gears, when driving along or 
coasting, there is noted a clattering noise. 
Upon sudden acceleration, or when the car is 
getting under motion, this is usually not notice¬ 
able. Gears that have not enough clear¬ 
ance, or that are meshed too tightly, howl and 
groan, this being very noticeable on sudden 
acceleration or when pulling a heavy load. 

When adjusting these gears, it is necessary 


that the back surface of the two gears line 
up properly. If one gear projects beyond the 
other only a few thousandths of an inch, the 
gears will be noisy, regardless of the amount 
of clearance. This adjustment is the align¬ 
ment adjustment of the pinion and should be 
made first. After these gears are lined up 
properly, then the clearance can be adjusted 
by either the adjusting nuts which are pro¬ 
vided for moving the ring gear to the right or 
the left, or by the space which is provided for 




FIG. 135 

FULL FLOATING AXLE WHEEL MOUNTINGS 


. (A-A) 

A. Hub cap. 

B. Jaw driving clutch. 

C. Wheel bearing adjusting nut and retainer. 

D. Wheel hub. 

E. Wheel hub flange. 

F. Bearings. 

G. Axle tube. 

H. Axle housing. 

I. Felt washers. 

J. Spokes. 

ILLUSTRATION A-A 

To remove the axle shaft from the housing, first re¬ 
move the hub cap (A) by unscrewing it, after which the 
axle shaft can be pulled out. The nut (C) is used to 
adjust the wheel bearings as well as hold the wheel 
on the axle housing. 


(B-B) 

A. Hub cap. 

B. Retainer. 

C. Washer. 

D. Tapered axle shaft. 

E. Wheel driving flange. 

F. Key. 

G. Wheel bearing adjusting nut and retainer. 

H. Bearings. 

I. Felt washer. 

J. Wheel hub. 

K. Axle housing. 

L. Axle tube. 

M. Spokes. 

ILLUSTRATION B-B 

To remove the axle shaft, take off the flange nuts, 
after which the hub and axle shaft can be drawn out of 
the housing. 



































































































182 


CHASSIS 


placing shims behind the thrust bearing on 
each side of the differential housing. After ob¬ 
taining the correct clearance, the adjuster for 
end play should be locked on each side of the 
differential case. The differential assembly 
should have about two-thousandths of an inch 
end play, and at the same time the ring gear 
and the pinion gear should have the proper 
clearance. The drive pinion is moved toward 
or away from the beveled ring gear either by 
an adjdsting nut or sleeve which holds the 
bearings or by the aid of the spacing shims. 

The bearings employed in rear axles may be 
tapered roller, plain roller with end thrust bear¬ 
ings provided of either the plain or ball type, 
or the single or double annular ball bearings. 


If an adjusting nut is provided to move these 
bearings back and forth, a lock is also provided 
to hold the adjusting nut in place, preventing 
it from shaking loose by vibration. On the 
outer end of the axle housing a felt washer is 
provided. The purpose of this felt washer is to 
prevent the oil or grease from working out of 
the axle housing into the brakes. If oil gets 
into the brakes, they will not hold. Remove 
the felt washer, soak in glycerine and then re¬ 
place. The glycerine does not mix with the 
oil, but prevents the oil from penetrating 
through the washer. 

The oil or grease that is used in the rear 
axle is 600-W oil or light cup grease. Fill 
the axle housing one-third full. This is sufR- 



FIG. 136 

THREE-QUARTER FLOATING AXLE, WITH SPECIAL 
WHEEL MOUNTING 


A. Brake drum. 

B. Brake drum hub. 

C. Rear axle housing. 

D. Rear axle shaft. 

E. Thrust washers (steel). 

F. Thrust washers (felt). 

G. Wheel bearing. 

H. WTieel driving hub. 

In this construction the wheel bearing is mounted on 
the axle housing and is held on by the nut (N). 

The main wheel driving hub (H) transmits the power 


I. Wheel driven hub. 

J. Axle shaft retaining nut. 

K. Spoke hub and retainer. 

L. Wheel hub retainer nut. 

M. Hub cap. 

N. Wheel bearing retainer nut. 

O. Spacing sleeve. 


from the splined axle shaft through driving pins (not 
shown) to the driven hub (I), which is held in place 
by the retainer nut (L). 































































REAR AXLES 


183 


;ient for the oil to be carried around by the 
;ears, lubricating all the gears and bearings, 
if the oil level is too high, there is a tendency 
'or the oil to be forced out past the felt washers 
it the end of the housing, where it will work 
nto the brakes. 

The axle shafts are made of high grade, heat 
treated alloy steel, and are usually finished 
)nly on the outer and inner ends. 

WORM DRIVE REAR AXLE 

The worm drive is used mostly on trucks 


and allows a greater ratio between speed of 
engine and speed of rear axles, resulting in 
more power. The worm drive is one of the 
most efficient drives, due to the lesser amount 
of friction on the bearing surface. The worm 
drive rear axle is generally of the full floating 
type, there being one main adjustment, which 
is the end play adjustment of the worm. The 
worm is usually made of low carbon steel, 
case hardened, while the worm wheel is made 
of high grade bronze. The worm wheel is 
bolted or riveted onto the differential housing. 



FIG. 137 


WORM DRIVE 


A. Axle drive worm. 

B. Rear bearing. 

C. PYont bearing. 

D. Axle drive worm gear. 

E. Adjuster lock. 

F. Felt washer. 

The adjustment on this type of drive is the adjuster 
(H), which removes the end play from the worm. To 
keep this nut properly adjusted, the lock (E) is pro¬ 
vided. The inner adjuster (G) is provided to adjust 


G. Felt washer adjuster. 

H. Worm front bearing adjuster. 

I. Rear axle housing. 

J. Grease fillet and level tube. 

K. Rear cover. 

L. Felt washer. 

the felt washer (F) which prevents the leakage of 
grease at this point. The washer should be soaked in 
glycerine. 
















































































Axle drive shaft flange. 


184 


CHASSIS 





















































































































































































































































FOUR WHEEL DRIVE 


185 


REAR AXLES 












































































































































































































































































































































186 


CHASSIS 


which is mounted on a set of bearings that are 
adjustable and that take both radial load and 
end thrust. 

The gear ratio of the worm and wheel drive 
is calculated by dividing the number of teeth 
on the worm wheel by the number of threads 
on the worm. The worm drive axle is lubri¬ 
cated by running the worm wheel in oil which 
supplies oil to the worm and bearings. Felt 
washers at the outer end keep the oil from 
working out. 


BRAKES 

The purpose of the brakes is to slow down or 
stop the car after the clutch is disengaged. 
The brakes may operate either directly on 
drums mounted on the rear wheels or on a 
drum fastened on the transmission shaft. 
There are usually two sets of brakes and in 
most cars they are both mounted on the rear 
wheels. One is known as the foot brake, 
and is controlled by the foot pedal, the other as 
the hand brake, and is controlled by the hand 






FIG. 140 






BRAKES 



A. 

Brake rod yoke. 

I. 

Outer brake band expanding 

Q. 

Inner brake band support. 

B. 

Hand brake rod.. 


spring. 

R. 

Adjusting screw. 

C. 

Outer brake band lever. 

J. 

Outer brake band spring rest. 

S. 

Spring. 

D. 

Inner brake shaft lever. 

K. 

Centering nut. 

T. 

Inner brake band. 

E. 

Inner brake toggle. 

L. 

Lock nut. 

U. 

Inner brake band lining. 

F. 

Inner brake toggle spring. 

M. 

Clevis. 

V. 

Brake drum. 

G. 

Inner brake stop. 

N. 

Pins. 

W. 

Outer brake band lining. 

H. 

Outer brake band adjusting nut. 0. 

Outer brake band support. 

X. 

Outer brake band. 



P. 

Inner brake band rest. 




When adjusting brakes, always adjust the brake bands 
as close to the drum as possible without binding or drag¬ 
ging, adjusting the clearance at the back first. Remove 
the cotter pin and turn the adjusting screw (R) forward 
into the stationary shaft (Q) to decrease the clearance. 
The clearance adjustment for the outer band is the 


same. After adjusting the clearance at the back, ad¬ 
just the clearance on the upper and lower half of each 
brake band. Screws (P) control the clearance of the 
inner brake band, adjusting nut (H) regulates the upper 
half of the outer brake band, while the lower half is 
adjustable through nuts (K). 




































BRAKES 


187 


brake lever mounted alongside the gear shift The foot brake should not engage until the 
lever. The foot brakes are, as a rule, mounted foot pedal is pushed halfway forward. The 
on the exterior of the brake drum fastened on- brakes are adjusted either by lengthening or 
to the rear wheel, and are of the contracting shortening the brake rods or by changing the 
type. The hand brake operates on the interior setting of the adjusting screw directly at the 
of the brake drum and is of the expanding type. band. 

On some cars one brake is mounted on the ' The hand brake should not take hold until 
rear wheels and the other on the transmission. 

The transmission brake may be either the 
foot brake or hand brake. Mounting the 
brake on the transmission shaft eliminates 
long brake rods and tubes and results in less 
noise and a cleaner chassis assembly. 

Sometimes the hand brake band is made of 
cast iron with no facing or lining, the lining 
being omitted for the reason that these brakes 
are not used as much as the foot brakes, al¬ 
though the majority have an asbestos facing. 

Due to the manner in which the hand brake 
is mounted, the rods that actuate it pass 
through the interior of a tube. This has a 
tendency to cause them to rust, due to their 
not being used often enough. A good plan to 
follow is to pull up on the hand brake every 
time the car is stopped, which is a good pre¬ 
caution against accidents and helps to prevent 
rust from gathering in this tube. 

The outer brake band has a lining made of 
asbestos and other materials. The lining is 
made fairly hard but still pliable, and resists 
wear and heat. It is held on the brake band 
with copper rivets. When riveting this lining 
onto the bands, the heads of the rivets should 
not be exposed, as they will cut the brake drum. 

If this happens, it is impossible to keep the 
brake linings on the bands for any length of 
time, due to the rough surface cutting and 
tearing them. 


FIG. 141 


FOOT AND HAND BRAKE CONTROLS 


A. 

Brake rod yoke. 

I. 

Intermediate shaft. 

B. 

Brake rod yoke. 

J. 

Intermediate shaft lever. 

C. 

Foot pedal. 

K. 

Intermediate shaft lever. 

D. 

Hand lever. 

L. 

Intermediate shaft. 

E. 

Brake rod. 

M. 

Intermediate shaft lever. 

F. 

Brake rod. 

N. 

Intermediate shaft lever. 

G. 

H. 

Right and left threaded turnbuckle. 
Lock nut. 

0. 

Frame. 


This illustration shows the foot and hand brake lock nut (H) prevents it from coming loose, 
connections and adjustments. The turnbuckle (G) is The rod (E) has a right and left hand thread and 
used to adjust the length of the brake rod, and the can be used to change the position of the hand lever. 


the hand brake lever has been pulled back at 
least half of its full travel, thus preventing the 
brake from dragging when the lever is for¬ 
ward. 

Using Engine as Brake 

When traveling through hilly country or in 
case the foot and hand brakes fail, the engine 
may be used as a brake. This also relieves 
regular brakes and prevents them from over¬ 
heating or burning. 

To use the engine as a brake, shift the gears 
to either second or low speed and shut off the 
ignition. The car will then be driving the 
engine, and the engine working against the 
compression will tend to resist and retard the 
movement of the car. 










188 


CHASSIS 


Troubles and Remedies 

Dragging brakes may be caused by improper 
adjustment, insufficient pressure of the re¬ 
tractor or brake band springs, brake members 
out of alignment or worn wheel bearings. 
Check the alignment of the bands and brake 
drum. If the drum is out of round, or the drum 
and brake band are not concentric the brake 
will drag at one point. A centering adjustment 
is provided for this purpose. If the wheel 
mounting is loose, the brake will also drag. 

The brakes and controls must be so adjusted 
that the right and left brakes are applied at the 
same time with equal pressure, that is, equal¬ 
ized. If the brake is applied only on one wheel, 
the car is more likely to skid and an excessive 
strain is thrown on the final drive. 


ing with new pins, clevis, etc., or by pressing 
in a new bushing where needed. 

Chattering brakes may be caused by the 
above mentioned parts becoming worn, lack 
of tension in the releasing springs, or the 
.spring clips not properly adjusted. 

Squeaking brakes are usually caused by 
the lining becoming worn, dirty or glazed. To 
remedy this, clean the lining with a stiff brush 
and kerosene, or replace with new lining. 

Do not apply the brakes too severely. Con¬ 
trol the speed of the car with the throttle as 
much as possible. 

SPRINGS 

The springs that are used on the present 
day cars are of the built up leaf type. The leaf 


BRAKES 



Axle Shaft 


FIG. 142 


Wheel Bearing 


Outer Brake Band 


Inner Brake Cam 


Inner Brake Band 


Outer Brake Band 
Adjusting Nut 


Inner Brake Band Springs 


Outer Brake Band 
Centering Nut 


Slipping brakes may be caused by an oil 
soaked lining, worn lining or improper adjust¬ 
ment. The controls should be adjusted so that 
the brake is applied when the control pedal or 
lever moves one-half of its travel, and should 
stop the brake drum before they have moved 
their full travel. To remove oil from the 
lining, clean with kerosene. Fuller’s earth may 
be used to absorb the oil. 

Sticking brakes may be caused by lack of 
lubricant on the brake mechanism, toggle, 
tube, shaft, lever, pins, clevis, etc. The rust 
and dirt should be removed from these operat¬ 
ing parts and lubrication applied freely. Ex¬ 
cessive wear of these parts will sometimes 
allow the brake to lock by moving past the 
center line. This can be remedied by replac- 


spring has proven more successful than the 
coil springs, and there is less liability of break¬ 
age. These springs are divided into several 
different types; namely, one-quarter elliptic, 
semi-elliptic, three-quarter elliptic, full elliptic, 
cantilever, and platform. 

In time the springs will squeak, due to the 
surfaces between the leaves becoming dry 
from lack of lubrication. To remedy this 
without removing the springs from the axles 
and frame, separate the spring leaves and 
squirt kerosene between them, which will 
loosen the rust. Then operate the car for about 
a day. Separate the leaves again and apply 
a mixture of graphite and oil between the 
leaves. Oil used alone will gradually dry out 
and be ineffective, while the graphite has a 







QUARTER ELLIPTIC 




FIG. 143 

SPRINGS 



















































190 


CHAS SIS 


tendency to fill the porous surface of the rough 
steel and stay between the surfaces. The best 
way to remedy a squeaking spring, caused by 
rust between the leaves, is to remove the 
springs from underneath the car, separate the 
leaves entirely by disassembling the spring and 
remove the rust with a wire brush, or emery 
cloth, and kerosene. When assembling them, 
apply graphite and oil between the leaves. The 
springs will wear very fast if not lubricated 
properly. 

The ends of the springs have bronze bush¬ 
ings pressed into them to receive the shackle 
bolt. The shackle bolt is hardened and ground 
and has a hole drilled in it to admit the lubri¬ 
cant from the grease or oil cup directly onto 
the bushing. When fitting these bushings and 
shackle bolts, they should be reamed to a snug 


fit, so that the bolt can just be pushed in with 
the palm of the hand without any play. 

MUFFLER 

The purpose of the muffler is to deaden the 
noise of the explosion as the exhaust gases 
escape. Mufflers are of many designs, some 
having greater tendency than others to hold 
back the exhaust and cause a back pressure in 
the exhaust pipe and cylinder. This back pres4 
sure being effective on the head of the piston, 
has a tendency to slow down the engine. Some 
mufflers are more efficient than others. Car¬ 
bon from the burned gases accumulates in 
the muffler, decreasing the area of the open¬ 
ings and causing back pressure. 

One common trouble with mufflers is that of 
internal explosions, which are caused by un- 




MUFFLERS 







































































IVTUPFLER — TIRES 


191 


burned gases passing out of the cylinder and 
gathering in the muffler, where they are ig¬ 
nited by the hot gases passing through. 1’his 
may be caused by cutting off the ignition and 
then turning it on again while the engine is 
still running. Cutting off the ignition when 
the engine is in operation causes the charge 
of fuel, which is not burned, to be forced out 
through the exhaust port into the muffler. 
When the ignition is turned on again, this gas 
ignites, often resulting in bursting the muffler. 

Mufflers can easily be disassembled by re¬ 
moving the stay bolts and taking the sections 
apart. Scrape the carbon out, clear the pas¬ 
sages and then reassemble. 

A cut-out may be provided in the ex¬ 
haust pipe between the muffler and the engine. 
It is noticeable that when the cut-out is opened, 
the engine usually increases its speed due to 
the reduction of the back pressure in the ex¬ 
haust pipe. The cut-out is made in various 
types, but all operate upon the same principle, 
the function being to provide an opening 
in the exhaust pipe for the purpose of al¬ 
lowing the exhaust gases to escape with less 
resistance. The cut-out is usually controlled 
by a foot lever close to the clutch pedal, which 
can be left open or closed at the will of the 
operator. 

CARE OF TIRES 

Proper care of the tires is necessary to be 
assured of uninterrupted service and also to 
keep down expense. 

There are certain common sense rules which 
apply to the proper maintenance of the three 
main parts of a tire, the casing or body, tread, 
and tube. 

Care of Casing 

The casing or body gives strength to the tire 
as long as the cords or the fabric remain un¬ 
broken. 

The most common cause of a broken casing 
is under-inflation. Keep the tires inflated to 
about eighteen pounds for each inch of tire 
width on fabric tires, and about fifteen pounds 
on cord tires. 

An average that can be used for fabric tires 
is as follows: 


30 

X 

3 . 

.55 

pounds 

30 

X 

31/2 . 

.60 

u 

32 

X 

3 ^'2 . 

.65 

(( 

32 

X 

4 . 

.70 

(( 

34 

X 

4 . 

.75 

(( 

36 

X 

41/2 . 

.80 

(( 

36 

X 

5 . 

.90 



For cord tires allow about five pounds less. 


Keeping the air in the tires at these pressures 
results in a good compromise between easy 
riding and maximum mileage. 

When an under-inflated tire is used, the ex¬ 
cessive flexing or bending of sides of the cas¬ 
ing heats it up and destroys adhesion of the 
fabric or cord layers. These layers will weak¬ 
en, then separate and finally break around the 
inner ply, weakening the side walls and if 
not immediately repaired, will usually result in 
a blowout, which sometimes cannot be re¬ 
paired. If the injury is discovered before any¬ 
thing more than the inner plies are broken, a 
reliner may be cemented into the casing. If 
this is not possible, a boot can be placed on 
the inside to reinforce the side walls at the 
weak point. 

This trouble can be prevented by maintain¬ 
ing the proper air pressure. Test the pressure 
with a reliable gauge at least once or twice a 
week. 

When driving regularly or when touring, 
test the pressure every morning. In case of 
tire trouble on the road, do not drive the car 
with the tire flat, even for a hundred yards, for 
the casing will be mashed between the steel 
rim and the road, and the tube will be cut 
so that it is practically impossible to properly 
repair either. 

“Fabric breaks” in the casing, caused by 
under-inflation, may not extend around the 
tire parallel with the rim, but across diagonally 
from one rim to the other. An injury of this 
kind is called a bruise, and it results from 
sudden shocks when tires strike stones, curbs 
or holes in the road, when travelling fast. To 
prevent “fabric breaks,” and keep the tires 
properly inflated, drive slowly over rough 
roads. 

For making roadside repairs of “fabric 
breaks,” use a cord patch or rim cut patch 
applied with one coat of cement inside, so that 
it can be removed and a vulcanized repair 
made later. Another method is to place a boot 
inside the casing, allowing the edge of the boot 
to clamp between the tire and rim when 
mounting. 

The tough tread or rubber covering of the 
casing gives the tire its wearing quality. 
Though the tread rubber is tough, it may oc¬ 
casionally be cut by some sharp object, such 
as a stone or a piece of glass. These small 
cuts should be repaired as soon as possible. 
If they are neglected, dirt, sand and water will 
work through them, rotting the casing, and 
finally cause a blowout. Clean these places 
and repair with tire putty or by vulcanizing 
them. 

An unusual jolt or strain, caused by bump¬ 
ing a curb, striking a rise or hole in the road 













192 


CHASSIS 


or scraping along curbs, may result in misa¬ 
lignment or wobbling of the wheels, or both. 
Then rapid tread wear results, because the 
wheel no longer runs true with the one oppo¬ 
site, but instead, travels over the road with a 
diagonal grinding motion. To check the proper 
alignment of the front wheels, check the toe-in 
or gather. 

To prevent scraping off the tread, always 
apply the brakes gradually. When the brakes 
are applied suddenly, they may lock and the 
tires be dragged over the pavement or roadway 
for several feet. 

The brake bands on both wheels should be 
adjusted equally, otherwise all the work of 
stopping the car is done by the wheel with 
the tighter brake, causing the tire on this 
wheel to be subjected to abnormal wear. 

Engaging the clutch too suddenly is another 
cause of worn treads, causing the tires to spin 
before obtaining a grip on the road surface. 

When the rubber on the side walls of a tire is 
scraped off by ruts or curbs, the cord or fabric 
underneath will soon rot if exposed to the 
dirt and moisture. Repair small side wall cuts 
while still new by vulcanizing or with tire 
putty. 

Apply chains loosely, because if applied too 
tightly, the cross chains strike the tire always 
at the same spot and will soon cut into the 
tread. 

If chains are applied on one wheel only, it 
will cause the other to spin and its tire to wear 
excessively. 

Do not reverse the chains by putting the 
worn side next to the tires, as the edges of the 
chains, sharpened by use, will cut into the 
tread. Remove chains as soon as possible 
after the emergency for which they were ap¬ 
plied is passed. 

Always protect tires as much as possible 
from excessive heat and light, both of which 
tend to harden the tread and make it wear 
more rapidly. 

Spare casings should be carried in tire 
covers. 

Do not let the tires stand in oil on the garage 
floor, as oil and grease cause the tread to rot, 
stretch and pull loose. Use gasoline to remove 
the oil and grease. 

Driving on car tracks is not advisable, due 
to the fact that only a portion of the tread 
of the tire runs on the rail and supports the 
load. A groove is worn around the tread 
where the edge of the track comes in contact 
with the tire, and the casing underneath is 
weakened. The car rails are frequently splin¬ 
tered by continued hard use and these splinters 
or the rough edges of the rails may easily cause 
bad cuts or punctures. 


Keep the spare tubes protected. They will 
become unfit for service by jostling around in 
their cardboard container, or by being loose in 
the tool box. The tube may become cut by 
sharp objects in the tool box, or may rot as a 
result of contact with oil and grease. Fold 
the tubes, dust with soapstone or French Talc, 
then wrap them in a cloth or place in a tube 
bag to prevent depreciation. 

When applying a tire, see that there is no 
dirt or rust on the rim. Examine the inside of 
the casing for fabric breaks, nails, dirt, or other 
foreign matter which may injure the tube. 

Dust the inner surface of the casing with 
mica, soapstone, or French Talc to Teduce 
friction between the tube and casing. Do not 
use too much of these powders, as they will 
cake in one spot and chafe the tube. 

Inflate the tube slightly and place it straight 
in the casing, making sure that the flap, if used, 
is not old and covered with rust. See that the 
tube does not slip under the bead so that it will 
be pinched between the bead and rim. When 
using tire irons, be sure that they are smooth. 

Valve leaks can be largely prevented by 
screwing the valve caps on tightly after inflat¬ 
ing or testing the tubes. The cap keeps out 
dirt and assists in holding the air in, should 
the plunger leak. 

CARE OF CAR IN STORAGE 

Wash and polish the body and cover it with 
a tarpaulin to prevent the dust, oil and light 
from marring the finish. 

Drain the water from the cooling system. 

Remove the spark plugs and pour two or 
three tablespoonfuls of clean cylinder oil into 
each cylinder. 

Clean the plugs, dip the ends in oil and re¬ 
place in the cylinders, after which crank the 
engine for twenty or thirty seconds with the 
ignition off. As the starter spins the engine, 
the oil is distributed over the cylinders, valves, 
etc., preventing rust. 

Exposed and unpainted metal parts of en¬ 
gine, body, and chassis should be well greased 
with vaseline to prevent corrosion and rusting. 
This can be removed with gasoline before put¬ 
ting the car back in service. 

Tires that are out of service for any length 
of time should be removed from the rims. The 
inner tubes should be put in the casings, par¬ 
tially inflated, and the tires stored in a moder¬ 
ately heated room away from the light, or the 
tires may be left on the rims, partially inflated 
and the car jacked up so that no weight is 
allowed to rest on them. 



SUMMARY 


193 


SUMMARY 


BEARINGS 

Types: 

Babbitt bearing. 

Bronze bearing. 

Plain roller bearing. 

Tapered roller bearing. 

Flanged roller bearing. 

Cup and cone bearing. 

Single Row annular bearing. 

Double Row annular bearing (rigid). 

Ball thrust bearing. 

Plain thrust bearing. 

Strains 

The babbit or bronze bearing, governed by 
its mounting, will carry both thrust and radial 
load. 

The plain roller bearing is designed to carry 
radial load only and is slightly adjustable. 

The tapered roller bearing is designed to 
carry both thrust and radial loads and is ad¬ 
justable. 

The flanged roller bearing is designed to 
carry both thrust and radial load and is slight¬ 
ly adjustable. 

The cup and cone bearing is designed to 
carry both thrust and radial loads and is ad¬ 
justable. 

The single row annular bearing is designed 
to carry radial load, but governed by it’s 
mounting, may carry radial only or radial and 
some thrust. It is not adjustable. 

The double row annular bearing is de¬ 
signed to carry both thrust and radial loads, 
governed by its mounting—not adjustable. 

The ball thrust bearing is designed to carry 
thrust load only and is adjustable. 

The plain thrust bearing is designed to carry 
thrust load only and is adjustable. 

Thus (not considering the bronze and bab¬ 
bit), there are seven bearings that will carry 
some thrust load. 

Six of these bearings will carry some radial 
load, the ball and plain thrust bearings being 
exceptions. Five of them will carry some 
thrust and radial load, the plain roller, ball 
and plain thrust bearings being exceptions in 
this case. 

Three of these bearings will carry both 
thrust and radial load. 

FRONT AXLES 

Types: 

Tubular. 

I-Beam. 

The purpose of the caster effect in the front 
axle mounting is to reduce vibration and steer¬ 


ing strains, and produce a “trailing” action 
that will cause the car to follow the road more 
easily. 

The purpose of the steering knuckle is to 
provide a movable mounting for the front 
wheel, that will permit its turning to control 
direction in which the car travels. 

The steering knuckle is controlled by the 
knuckle arm, acting through the knuckle 
thrust arm, which is controlled by the thrust 
rod or connecting rod from the steering de¬ 
vice. 

The purpose of the pivot bolt or pin is to 
provide a swivel mounting for the steering 
knuckle in the axle yoke, to permit turning of 
the spindle for steering. 

The purpose of the camber of the front 
wheels is to reduce the distance from the point 
of wheel contact on the road to the center line 
of the pivot bolt, bringing the arc of wheel 
travel, when steering, nearer the axis of the 
bolt. This reduces steering strain, since the 
strain that has to be overcome by the driver, 
acting through the steering device, is the fric¬ 
tion of the tires on the road multiplied by the 
distance traveled by the wheel around the axis 
of the pivot bolt. Camber also reduces wear 
on tires. 

The amount of camber is governed by the 
wheel mounting and diameter of the wheel. 

The camber is not adjustable. The approxi¬ 
mate camber for large cars will be from 1° to 
2°, on medium size cars 3°, and on small cars 
from 4° to 5°. 

The purpose* of “toe in” or “gather” is to 
counteract the tendency of the front wheels 
to roll outward or pull apart in front, due to 
the camber. 

The toe in or gather is adjustable. When 
the tie rod is located behind the axle, to in¬ 
crease the gather, lengthen the tie rod; to de¬ 
crease it, shorten the tie rod. 

When the tie rod is located in front of the 
axle, to increase the gather, shorten the tie 
rod; to decrease it, lengthen the tie rod. 

The amount of gather is governed by the 
amount of camber. On the average large car, 
allow 1/4" gather, on the medium size cars, 
allow 5/16", and on the smaller cars, allow 
3/8". 

Thus: 

Camber Gather 

1° - 2° i inch 

3° inch 

4° - 5° t inch 





194 


CHASSIS 


The purpose of the tie rod is to connect the 
steering knuckle arms and adjust the gather. 

To check the alignment of the knuckle arms 
on the average car, two lines drawn, one 
through the center of each knuckle arm, should 
cross approximately in the center of the rear 
axle. 

Thus, the angle at which the knuckle arm is 
set is governed by the wheel base of the car, 
and the angle of the knuckle arms governs the 
difference in travel of the two spindles around 
their axes, which in turn governs the distance 
required to make a complete turn, or the turn¬ 
ing radius. 

To prevent play developing between the 
steering arm of the steering device and the 
front wheels, it is necessary to adjust and 
lubricate the following: the ball and socket 
joints of the thrust rod, the tie rod and 
knuckle arm connections, the pivot bolt, the 
steering knuckle, and the front wheel mount¬ 
ings on the spindle. 

If these different points are not properly 
adjusted, the wheels will have a tendency to 
wobble. Sometimes the wheels wobble even 
though these different points are properly ad¬ 
justed. This is caused by the wheels becoming 
sprung or warped. This can be remedied by 
straightening the wheels under a press or by 
replacement. 

STEERING DEVICES 

Types: 

Reversible — Planetary. 

Reduction Gear. - 

Irreversible—Worm and Wheel. 

Worm and Sector, 

Split Nut or Jay-Cox. 

Worm and Nut. 

Worm Screw and Nut. 

Adjustments: 

Planetary—No adjustment. 

Reduction Gear—No adjustment. 

Worm and Wheel—Three adjustments. 

Worm and Sector—Two adjustments. 

Worm and Nut—One adjustment. 

Jay-Cox or Split Nut—One adjustment. 

Worm Screw and Nut—One adjustment. 

CLUTCHES 

Types: 

Cone: 

Single Spring. 

f Lubricated 

Disc: j Multiple Spring. 

I Dry 

Plate. 

The purpose of the clutch spring is to hold 
the driving and driven members together when 
the clutch is engaged. 


The purpose of the clutch brake is to stop 
the revolving driven member after the clutch 
is disengaged, thus allowing easier shifting of 
the transmission gears. 

The purpose of the facing springs and 
plungers is to force the facing away from the 
cone when the clutch is disengaged. This 
helps to make a smooth and gradual engage¬ 
ment of the clutch. 

There is no function of the springs and 
plungers after the clutch is engaged. 

Clutch Troubles: 

Slipping. 

Grabbing. 

Spinning. 

Dragging. 

Stuttering. 

Cone and Dry Disc Type 

Slipping: Spring tension weak; worn clutch 
facing; warped cone; oily or greasy facing; 
clutch shaft out of line; release mechanism out 
of adjustment. 

Remedy: Increase spring pressure; renew 
facing; replace cone; clean facing with kero¬ 
sene, temporarily apply Fuller’s Earth or 
talc; replace bearings; check up operating 
mechanism. 

Grabbing: Too sudden engagement; rivets 
exposed; facing dry and hard; facing springs 
improperly adjusted; excessive spring tension. 
Remedy: Engage more gradually; countersink 
rivets; renew facing or clean and roughen with 
emery cloth and apply Neat’s foot oil; adjust 
facing springs; relieve spring tension. 

Spinning: Examine the condition of the 
clutch brake. 

Dragging: Lubricate the tail shaft. 

Check up clutch operating mechanism to see 
that it permits full release of clutch. 

Stuttering: Replace the radial bearing, or 
adjust the clutch release fork. 

Lubricated Disc 

Dragging: Caused by heavy or gummed 
oil. Remedy: If the clutch is lubricated in¬ 
dividually, add about one-third the amount of 
kerosene to the clutch oil or use a lighter oil. 
If the clutch is lubricated from the engine, 
drain the oil, clean the clutch with kerosene 
and replace with the correct grade of oil 
recommended for the engine. Never add kero¬ 
sene. 

TRANSMISSIONS 

Types: 

Progressive. 

Selective. 

Planetary. 

There are eight gears in the standard three 




S U M M A R Y 


195 


speed forward and one reverse selective or 
progressive transmission. 

The progressive transmission has a lock on 
the shifting lever that locks it in the different 
positions. This prevents the sliding gears from 
working into or out of mesh. 

In the progressive transmission the two 
sliding gears are integral and the gears are so 
spaced in the transmission that it is impos¬ 
sible to have both sliding gears in mesh at the 
same time. 

The selective transmission is equipped with 
a gear lock and sometimes an interlocking de¬ 
vice. The purpose of the interlocking device 
is to prevent the shifting of two sets of gears 
into mesh at the same time. The purpose of 
the gear lock is to lock the shifting bars and 
sliding gears, thus preventing the gears work¬ 
ing out of or into mesh due to vibration. 

To determine the engine end of a trans¬ 
mission, place the shifting lever in low, second 
or reverse, and turn either one of the project¬ 
ing shafts, which will result in driving the 
other. The shaft that revolves the faster will 
be the clutch shaft or engine end. 

When checking the alignment of gears and 
shafts, always check from the transmission 
drive or clutch gear. 

In a selective or progressive transmission 
with three speed forward and one Reverse, 
when driving in low, there are six gears in 
mesh and the power is transmitted through 
four. When driving in second, there are six 
gears in mesh and the power is transmitted 
through four. In reverse, there are five gears 
in mesh and the power is transmitted through 
five. When driving in high, there are four 
gears in mesh, and power is transmitted 
through the high speed dogs or the internal 
clutch gear. 

To determine the gear shift arrangement of 
any three speed forward and one reverse selec¬ 
tive transmission, place the shifting iever in 
different positions until reverse is obtained. 
Always on the same side, but on the opposite 
end, will be low, and diagonally across from 
low is second, on the same end as reverse. On 
the same side as second, but on the opposite 
end, is high. 

On the Ford planetary transmission, there 
are always twelve gears in mesh. When the 
gears become worn, the transmission is very 
noisy, due to the numerous gears not being in 
proper mesh. 

When driving in low or reverse, the power 
is transmitted through the triple gears, which 
revolve on their axes. There is no power 
transmitted through the tail shaft. 

When driving in high, the power is trans¬ 
mitted directly through the tail shaft and clutch 


discs. There is no power transmitted through 
the triple gears. 

When assembling the clutch discs, always 
begin and end with a large or driven disc. That 
is, place a large disc in the brake or driving 
drum first, then a small one, then a large one, 
and so on alternately, ending with a large disc, 
after which place the push ring against the 
last large disc. 

When assembling the triple gears, use care 
to see that the gears are properly meshed. 
The teeth on the three triple units are in 
line at three points and are usually marked 
at one of the points on the twenty-seven 
tooth gear. Mesh the marked point of the 
twenty-seven tooth triple gear with the 
twenty-seven tooth driving gear, and exactly 
nine teeth each side of that point, mesh the 
two remaining sets of triple gears according to 
marks. This places the three sets of triple 
gears at equal distances of 120°. 

When starting in low or reverse, allow the 
revolving drums to slow down gradually as 
the band is compressed around the drum. This 
friction lined band acts as a clutch to pro¬ 
vide flexibility for starting by allowing a cer¬ 
tain amount of slippage. If these bands are 
applied too suddenly, the car will jerk when 
starting, the same as when the clutch is en¬ 
gaged too quickly on any car. Grabbing may 
be caused by the rivets being exposed, the fac¬ 
ing being hard or adjusted too tightly, or the 
drums being rough. 

Slipping may be caused by the facings 
being worn, or the bands being adjusted too 
loosely. The brake and reverse bands should 
be adjusted so that the foot pedal can move 
one-third forward before the band comes in 
contact with the drum. This is to prevent 
dragging and wearing of the facing and drum 
when the pedal is all the way back. When 
the foot pedal is pressed two-thirds the way 
forward, the band should be contracted enough 
to stop the drum from revolving. This same 
adjustment will hold true on the low speed 
band and drum, except that the band should 
be adjusted to contract and stop the revolving 
of the drum about three-fourths the way for¬ 
ward. To adjust the brake and reverse bands, 
the transmission cover plate will have to be 
removed. The low speed band can be ad¬ 
justed from the outside. 

Due to the construction of the transmission, 
two units will revolve, unless both engine and 
rear wheels are stationary. If the engine is 
running and the rear wheels are stationary, 
the stationary twenty-seven tooth driven gear 
will drive the triple gears on their axis, and this 
will drive the low and reverse drums around 
idle inside the bands. If either the low or 



196 


CHASSIS 


reverse drum is held stationary, the twenty- 
seven tooth driven gear will revolve and drive 
the rear wheels. If the engine is not running 
and the rear wheels revolve, the twenty- 
seven tooth drive gear will drive the drums 
through the triple gears. 

The purpose of the clutch lever screw that 
rides on the clutch lever cam is to adjust the 
neutral position of the clutch. That is, if this 
screw becomes worn, when the hand lever is 
pulled half way back, the clutch shifting collar 
will not be moved back enough to disengage the 
clutch. To remedy this, turn the screw inward 
at the cam until neutral is obtained. 

If this screw is turned down too much, 
when the hand lever is moved all the way for¬ 
ward the cam screw may still ride on the cam 
and prevent the full engagement of the clutch, 
which will cause slippage. To remedy this, 
loosen the screw at the cam. 

If the clutch slips, increase the spring pres¬ 
sure with the clutch spring adjusting screws 
in the clutch fingers. The purpose of the con¬ 
necting link is to adjust the clutch pedal so 
that it corresponds with the hand lever move¬ 
ment. That is, when the hand lever is all the 
way forward, the clutch pedal should move 
all the way back. When the hand lever is half 
way back, the clutch pedal should not move 
forward to the extent that the band will hold 
the drum stationary. If this occurs, it will be 
difficult to obtain neutral. 

If the controls are properly adjusted and 
the clutch still drags or neutral cannot be 
obtained, the most probable cause is that the 
oil is too heavy or is gummed. To remedy this, 
clean the clutch with kerosene and replace 
with the correct oil for the engine. After 
using kerosene, remove the oil pan and all 
traces of kerosene. 

Planetary Transmission and Clutch Adjustments 

There are three points of adjustment on the 
transmission—the three transmission bands. 
There is one replacement on the transmission— 
shims or a new bushing between the brake or 
driving drum and the disc or clutch drum. 
This is to overcome end play. There are five 
points of adjustment on the clutch—the three 
clutch fingers or the spring adjustment screws, 
which are all for the same adjustment, the 
clutch lever adjusting screw at the cam and 
the connecting link. There are eight points of 
adjustment on the transmission and clutch. 

UNIVERSAL JOINTS 

The purpose of the universal joint is to 
transmit a revolving motion through shafts 
set at an angle with each other. 

The purpose of the flexible joint is to trans¬ 
mit a revolving motion through shafts set at 


an angle with each other, and to cushion the 
shocks and reduce vibration. The construc¬ 
tion of the flexible joint will permit of only a 
limited angle between the two shafts. 

The purpose of the slip joint is to compen¬ 
sate for the variation in distance between the 
rear axle and the transmission, caused by the 
movement of the springs when driving. 

TORSION STRAINS 

The purpose of the torque tube or rod is 
to brace the axle mounting against the ten¬ 
dency to revolve around its own axis when 
power is applied, thus preventing the torque 
strain from being thrown on the springs. 

When no torque tube or rods are used, the 
torque is taken by the springs and mountings 
and it is called a Hotchkiss drive. 

DIFFERENTIAL 

The purpose of the differential is to transmit 
the power from the drive or pinion shaft to 
the axle shafts and to both rear wheels equally, 
depending upon the resistance offered, and 
at the same time to permit the wheels revolv¬ 
ing independently when the car is turning a 
corner. 

Differential Action 

When driving straight ahead with both tires 
of the same size and inflated to the same pres¬ 
sure, each wheel will offer the same resistance, 
and for every revolution of the ring gear, each 
wheel will make a full revolution. 

When making a turn, the inside wheel offers 
the more resistance to the spider gears, which 
will cause the outside wheel to travel faster. 
If one wheel is held stationary, the other wheel 
will be driven twice as fast as the ring gear. 
If the ring gear is held stationary and one 
wheel is moved forward, the other wheel will 
be driven backward at the same speed. 

REAR AXLES 

Types of live axles: 

Plain live axle. 

Semi-floating axle. 

Three-quarter floating axle. 

Pull floating axle. 

Types of axle housings: 

Divided housing. 

Bell type housing. 

Types of final drives: 

Bevel gear. 

Worm gear. 

Chain drive. 

Internal gear. 

Types of final drive gears: 

Straight tooth bevel. 

Spiral tooth bevel. 

Worm. 



SUMMARY 


197 


Clearance between the teeth of the ring and 
pinion gear: 

Both gears new, allow .012" clearance. 

Both gears old, allow .006" clearance. 

One old and one new gear, allow .008" clear¬ 
ance.- 

Too much clearance will cause clattering of 
the gears. 

Insufficient clearance will cause growling 
gears. 

There should not be more than .002" end 
play in differential mounting. 

The ring gear should always be mounted on 
the left side of the pinion gear. If it is mounted 
on the right side, there are three speeds reverse 
and one forward. 

SPRINGS 

One-quarter elliptic. 

Semi-elliptic. 

Three-quarter elliptic. 

Full elliptic. 

Cantilever. 

Platform. 

BRAKES 

Inner, (hand operated), expanding. 

Outer, (foot operated), contracting. 

Brake Troubles: 

Dragging, Slipping, Sticking, Chattering, 
Squeaking. 

PRECAUTIONS AND DON’TS 

Don’t use pliers as a substitute for a wrench. 

Don’t use a cold chisel for removing a nut. 

Don’t “choke” a hammer, by grasping it too 
far up on the handle. 

Don’t bear down on a file or hacksaw on 
the back stroke. 

Don’t wipe the filings off the work with your 
hand. 

Don’t allow a drill to become hot when 
sharpening. 

Don’t use a monkey wrench for a hammer. 

Never draw a monkey wrench away from 
the jaws, but towards them. 

Keep your tools orderly arranged. 

Don’t use a tap or die without oil—except 
on brass and copper. 

Don’t grind one lip more than the other 
when sharpening a drill. 

Don’t turn a drill or reamer backwards. 

Always run an expansion reamer all the way 
through the hole. ' 

Always see that bearings are perfectly clean 
before mounting. 

Don’t fit bearings so tightly that they will 
bind. 

Don’t fit bearings so loosely that they will 
pound. 


Don’t drive a bearing into its mounting. 

Always remove the sharp edge of a bushing 
before pressing it into the hole. 

Always remove the sharp edges of the hole 
before pressing the bushing into it. 

Keep the front wheels adjusted. Examine 
the thrust rod and the tie rod connections occa¬ 
sionally. 

Don’t turn the steering wheel unneccessarily 
when the car is stationary. 

Don’t assemble a Jay-Cox steering gear with 
the half nuts transposed. 

Don’t engage the clutch too quickly. 

Keep your foot off the clutch pedal when 
driving. 

Don’t slip the clutch unnecessarily. 

Don’t run a lubricated type clutch without 
the proper lubrication. 

See that the facing rivets are properly 
countersunk on the cone and dry disc clutch, 
as well as on transmission and brake bands. 

Don’t try to shift the gears in or out of mesh 
without first disengaging the clutch. 

Don’t speed up the car too much before shift¬ 
ing into high. 

Don’t overload the engine by trying to make 
a hard pull in high. Shift to a lower speed. 

Always know the position of reverse before 
shifting into the different speeds. 

On a selective transmission, when shifting 
from a low to a higher speed, accelerate the 
car, disengage the clutch, allow the clutch 
brake to slow down the counter shaft for an 
instant, shift the gears into mesh and engage 
the clutch. 

When shifting from a higher to lower speed, 
disengage the clutch and shift the gears into 
mesh, then again engage the clutch. 

Never shift into reverse without allowing the 
car to* come to a stop. 

Don’t press on the low or reverse pedal of a 
Ford car too quickly. Force the pedal forward 
slowly until a movement is started, then hold 
it all the way down. 

Always see that the pinion shaft and differ¬ 
ential adjustments are properly locked. 

Don’t drive with the tires under-inflated. 

Keep the shackle bolts lubricated and the 
shackles tight. 

Don’t apply the brakes too severely'. 

Never drive a car without testing the brakes. 

Don’t use one brake continuously. 

When coasting down a hill, alternate or use 
the compression of the engine. 

See that the brakes are equalized, especially 
if the road is slippery. 

Don’t take chances unnecessarily. 




198 


CHASSIS 


DRIVING 


Complete control of the car while driving is 
necessary at all times to prevent accidents. 

To have this complete control requires con¬ 
fidence in yourself and the car. This can only 
be obtained by knowing the car and its me¬ 
chanical appliances thoroughly. 

The various parts of the car, such as the 
engine, clutch, brake, etc'., must be in perfect 
working order and sensitive in action for per¬ 
fect control. 

The driver should be positive that there is 
sufficient oil in the engine, transmission and 
rear axle, also sufficient water in the radiator. 
In cold weather, a non-freezing compound 
should be mixed with the water in the radiator. 
See that there is sufficient gasoline in the tank. 
The tires should be inflated to the proper pres¬ 
sure. 

The gear shift should be thoroughly under¬ 
stood so that the driver will not shift the gears 
into the reverse speed with the car still moving 
forward, as this will break the teeth of the 
transmission gears. 

If the gear shift is not known, it can be de¬ 
termined by the following method: Allow the 
engine to run slowly, disengage the clutch, 
move the gear shift lever into one position after 
the other, each time engaging the clutch, until 
the reverse speed is found. Low will be on the 
same side, but on the opposite end, second 
speed will be on the same end as reverse, but on 
the opposite side, while third speed will be on 
the same side as second, but on the opposite 
end. This rule applies to the three speed selec¬ 
tive transmissions of modern automobiles and 
trucks. After the driver understands the gear 
shift, it is necessary to learn to control the 
clutch correctly. It must be prevented from 
grabbing suddenly, thereby spinning the tires 
on the road, breaking the propeller or axle 
shaft, or stripping the teeth of the transmission 
or differential gears. Again, if the clutch is 
allowed to slip too much when racing the en¬ 
gine, the clutching surfaces will be badly worn 
and require repairs. 

The purpose of the clutch is to disengage the 
engine from the transmission while shifting 
the gears into the different speeds and neutral. 
It also permits the power to be engaged grad¬ 
ually after the gears are in mesh. 

To start the car, allow the engine to run at 
a moderately low speed, then disengage the 
clutch and shift the gears into low, after which 
gradually engage the clutch, feeding gas a 
little at the same time to prevent the load from 
stalling the engine. This will cause the car to 


gain momentum. When the clutch is fully en¬ 
gaged, the speed of the engine should then be 
increased, as it will eliminate unnecessary slip¬ 
page when shifting the gears from low to sec¬ 
ond speed. 

To change from low to second gear: As the 
clutch is disengaged, allow the engine to slow 
down again, shifting the gears from low to 
second and engaging the clutch gradually with¬ 
out speeding the engine but feeding gas a little 
at the same time. When the clutch is fully 
engaged, the engine should be speeded up. 

Before changing the gears from second to 
high, it is again necessary to slow down the 
engine as the clutch is disengaged. After the 
gears are changed, engage the clutch. When 
the clutch is fully engaged, the car may be 
driven at the various speeds by controlling the 
speed of the engine. If the car will not pick up 
in speed after being slowed down, shift the 
gears to the lower speeds in preference to 
speeding the engine and allowing the clutch to 
slip. Never start the car in the intermediate 
or high speeds from a dead stop, as this causes 
too much slippage of the clutch. This is one 
of the reasons for equipping the car with the 
low speed gearing. Do not shift the gears into 
the lower speeds while the car is moving at a 
speed not requiring the use of the low speed 
gears. This can be accomplished only by in¬ 
creasing the speed of the engine to prevent the 
clattering of the gears. 

After the driver has mastered the operation 
of the car, it is necessary to become familiar 
with the rules and regulations of traffic, as 
drivers must govern themselves accordingly. 
With this knowledge, one may know what to 
expect of other drivers, though allowance must 
always be made for reckless drivers who do not 
follow or respect these rules. 

In driving the car, allow sufficient distance 
between your car and the one ahead, or at the 
side. Do not drive too close to the curb or the 
side of the road, because if it should be neces¬ 
sary to stop suddenly, there should be space 
enough to maneuver the car without bumping 
other cars. When passing another car, always 
pass upon the left side, and only after a warn¬ 
ing signal has been sounded. In turning into 
a side street, or when stopping the car, the 
driver should indicate this by a signal of the 
hand. 

The driver should always endeavor to protect 
the car and its accessories while driving. He 
should strive not to drive in the car tracks, or 


1 




DRIVING 


199 


rub the tires on the side of the curb while stop¬ 
ping, as this will wear and tear the plies of 
fabric, thereby subjecting the tires to unneces¬ 
sary damage. 

Accelerating the car too suddenly when not 
necessary, driving with the spark too far in 
advance or retard, or operating the car with 
the mixture too rich or too lean, causes a loss 
of fuel and power. 


The driver should study the car and its 
capabilities with respect to efficiency and 
economy, as this will give greater mileage and 
will save fuel, oil and tires. Any repairs neces¬ 
sary should be taken care of at once, and 
properly done by mechanics thoroughly 
famihar with the construction of the car. 
Neglect will cause unnecessary wear and 
greater expense. 



200 


CHASSIS 


QUESTIONS 


1. Name the different types of bearings 
used in the chassis and final drive. 

2. How tightly should a bearing be fitted 
on a shaft and in a housing? 

3. ■ Is it advisable to replace one new ball 
in a ball bearing? 

4. Is it advisable to carry thrust strains on 
a single row annular ball bearing? 

5. How tightly should a cup and cone or 
tapered roller bearing be adjusted? 

6. How many bearings are designed to 

carry some thrust load? 

7. How many bearings are designed to 

carry some radial load? 

8. How many bearings are designed to 

carry both thrust and radial load? 

9. How many bearings are designed to 

carry both thrust and radial load and are ad¬ 
justable? 

10. Name the types of front axles. 

11. What material is used in axle con¬ 
struction? 

12. By what two points and how is the 
alignment of the front axle checked? 

13. What is the purpose of the caster con¬ 
struction of front wheels and how is it ob¬ 
tained? Is it adjustable? 

14. What is the purpose of camber? 

15. What governs the amount of camber? 

16. What is the purpose of the toe-in or 
gather of the front wheels? 

17. How is the gather measured? 

18. How should the gather be adjusted? 

19. About how much camber will a medium 
sized car have and how much gather should be 
allowed? 

20. How is the alignment of the steering 
arms proven? 

21. When making a turn to the left, which 
wheel swings through the greater angle? 
Which wheel travels the greater distance? 

22. Why can a quicker turn be made with 
a car having a short wheel base than with a 
long wheel base? 

23. What will cause a front wheel to 
wobble ? 

24. How can this be remedied? 

25. Name the different types of steering 
devices. 

26. How many adjustments on a worm and 
wheel steering device? 

27. What is the purpose of the eccentric 
bushing? 

28. What two precautions should be ob¬ 
served when assembling a Jay-Cox or split nut 
steering device? 

29. What is the cause if, after assembling 


a Jay-Cox or split nut steering gear, the steer¬ 
ing wheel is turned to the right and the car 
moves to the left? 

30. How is this trouble remedied? 

31. What is a planetary gear set? 

32. Explain the action of the planetary 
steering device. 

33. When the steering wheel of a Ford 
steering gear is turned one-half revolution, 
how many degrees will the steering arm re¬ 
volve? 

34. How many adjustments are there on a 
Ford planetary steering device? 

35. What is the purpose of a clutch? 

36. What are the different types of 
clutches? 

37. How many types of cone clutches are 
there ? 

38. What advantages has the multiple 
spring over the single spring cone clutch? 

39. How much tension is required on any 
clutch spring? 

40. What is the purpose of the facing 
spring plungers? 

41. Is there any function performed by the 
spring plungers on a cone clutch, when the 
clutch is fully engaged? Disengaged? 

42. What advantages has the lubricated 
type disc clutch over the dry type? 

43. What is the main objection to a lubri¬ 
cated type clutch? 

44. Name the five common clutch troubles. 

45. What are the two most probable causes 
of a slipping cone clutch? 

46. What is a temporary remedy for a slip¬ 
ping cone clutch caused by an oil-soaked 
facing? 

47. How is a grabbing cone clutch in which 
the facing has just been replaced remedied? 

48. What is the most probable cause of a 
dragging cone clutch? 

49. How is a dragging lubricated type 
clutch remedied when the clutch is lubricated 
from the engine? 

50. What is the most probable cause of a 
stuttering clutch? 

51. What is the purpose of the clutch 
brake? 

52. Name the types of transmissions. 

53. What is the principal difference in con¬ 
struction between the progressive and selective 
transmissions? 

54. What is the standard number of gears 
for a three speed forward and one reverse 
progressive or selective transmission? 

55. When driving in low speed how many 
gears are in mesh? 




CHASSIS 


201 


56. When coasting down hill with the gear 
shift lever in second speed and the clutch dis¬ 
engaged, how many gears in the transmission 
are revolving? 

57. When the car is standing with the en¬ 
gine running, the clutch engaged and the gear 
shift lever in neutral, how many gears are re¬ 
volving? 

58. What prevents the shifting of two sets 
of gears into mesh at the same time on a car 
with the ball and socket gear shift lever? 

59. What holds the gears in mesh on a car 
with an “H” plate gear shift? 

60. What prevents the shifting of two sets 
of gears into mesh at the same time on a pro¬ 
gressive transmission? 

61. How is the engine end of a transmission 
determined? 

62. Suppose that the second speed gears 
will not stay in mesh in a selective transmis¬ 
sion, how can this be remedied? 

63. When driving a Ford car in low gear, 
is there any pulling strain on the tail shaft? 

64. Will the triple gears be rotating on their 
axes? 

65. When driving in low gear and the fly¬ 
wheel makes one revolution, what part of a 
revolution does the drive shaft make? 

66. How many revolutions of the flywheel 
are necessary to complete one revolution of the 
drive shaft when driving in low gear? 

67. When driving in high gear, is there any 
pulling strain on the triple gears? 

68. Will the triple gears be rotating on their 
axes when driving in high? 

69. Looking at the rear of the transmission, 
in which direction do the triple gears rotate on 
their axes when driving in low? In reverse? 

70. How many points of adjustment are 
there on the Ford planetary transmission? 

71. How many points of adjustment are 
there on a Ford clutch? 

72. How is the tension of the Ford clutch 
spring increased? 

73. If the hand lever of a Ford car is pulled 
half way back and the clutch is not disengaged, 
how is this trouble remedied? 


74. How is end play in a Ford planetary 
transmission overcome? 

75. What are the purposes of the universal 
joint, flexible joint and slip joint? 

76. What is the purpose of a differential? 

77. Which rear wheel offers the more resist¬ 
ance to the spider gears when making a turn, 
the inside or outside? 

78. If the left wheel is held stationary and 
the right wheel turned forward four revolu¬ 
tions, how many revolutions will the ring gear 
make and which way will the spider gears 
rotate on the spider? 

79. Suppose the right wheel is held station¬ 
ary while the ring gear is turning forward two 
revolutions. How many revolutions will the 
left wheel make and in which direction will the 
spider gears rotate on the spider? 

80. When making a turn to the left, in 
which direction do the spider gears rotate? 

81. If, after assembling an axle, there are 
three speeds reverse and one forward, what is 
the trouble? 

82. Name the types of rear axles and ex¬ 
plain the mounting of the bearings and the 
strains carried by the axle shafts. 

83. How many types of axle housings are 
there? 

84. What is the advantage of a spiral cut 
bevel gear over a straight tooth bevel gear? 

85. What is the most probable cause of a 
slipping brake? 

86. How is a chattering brake remedied? 

87. What will cause a brake to stick? 

88. How are squeaking springs remedied? • 

89. What will be the result if the brakes are 
not adjusted evenly? 

90. Would it be advisable to remedy a noisy 
brake by applying lubricating oil on the facing? 

91. What is the trouble if the brakes are 
adjusted properly when the wheels are off the 
ground and the brakes drag when the wheels 
are on the ground? 



202 


NOTES 


1 





> 






ELEMENTS OF ELECTRICITY 
AND IGNITION 


MAGNETISM 


Magnetism is the property that enables a 
magnet to attract iron and steel. The word 
magnetism is derived from “Magnesia,” the 
name of a province in Asia Minor, where it is 
thought magnetism was first discovered. Here 
the ancient Greeks found a peculiar iron ore 
which possessed the property of magnetism. 
This ore is called magnetite, sometimes lode- 
stone. Lodestone means “leading stone” and 
the ore was so named because use was made 
of it to guide ships at sea. An elongated piece 
of lodestone freely suspended comes to rest so 
that a certain point is toward the north and 
another point is toward the south. Lodestone 
is a natural magnet. 



A piece of iron or steel when stroked with a 
piece of lodestone becomes magnetized. See 
Fig. 201. Magnetized bars of iron or steel are 
called artificial magnets. Magnets made by 
magnetizing hardened steel are called perma¬ 
nent magnets because hardened steel remains 
magnetized indefinitely. Only thin bars of 
hardened steel can be magnetized with lode¬ 
stone; the larger bars are magnetized with 
strong electro-magnets, which will be described 
later. 

Magnetic Materials 

There are only a few materials which a mag¬ 
net will attract, or which can be magnetized. 
Such materials are called magnetic materials. 
Only iron and steel are magnetic to a degree 
of practical importance and are usually 
thought of as the magnetic materials. Nickel 
and cobalt are slightly magnetic. Bismuth is 
repelled by a magnet instead of attracted. It is 
said to be diamagnetic. 


Non-Magnetic Materials 

Materials which cannot be magnetized and 
which are not attracted by a magnet, are called 
non-magnetic materials. Examples:—Copper, 
bronze, aluminum, glass, rubber, etc. 

Poles 

The points of strongest attraction on a mag¬ 
net are called the poles. (See Fig. 202.) The 
pole that always seeks the north, when the 
magnet is suspended free to turn, is called the 
north pole and the pole that seeks the south 
is called the south pole. Every magnet has at 
least one north pole and one south pole. 



N 



FIG. 202 

Either pole of a magnet attracts unmagne¬ 
tized iron or steel with the same force. That 
is, the north pole of a magnet will lift as much 
as its south pole, or vice versa. 

The strength of a magnet’s attraction is in¬ 
versely proportional to the square of the dis¬ 
tance from its poles. That is to say, a mag¬ 
net will attract a piece of iron 1/4” from its 
poles with four times the force that it will at¬ 
tract the same piece of iron 1/2” from its poles. 

Law of Attraction and Repulsion 

Like poles repel, unlike poles attract. Repul¬ 
sion is illustrated in Fig. 204 and attraction in 
Fig. 205. 

Magnetic Lines of Force 

The exact nature of magnetism is not 
known. Magnetism is thought to flow along 
lines, called magnetic lines of force, which ex¬ 
tend from pole to pole of a magnet. The space 
surrounding a magnet through which the lines 
of force are said to flow is called the “mag¬ 
netic field.” The extent of this field is in¬ 
definite. However, the field becomes so weak 








204 


ELEMENTS OF ELECTRICITY 


as the distance from the magnet increases, that 
it soon becomes scarcely perceptible. 

The lines of force in a magnetic field can 
best be shown with iron filings. Place a piece 
of glass (or a cardboard) over a magnet and 
then sprinkle iron filings on it. As the iron 
filings drop upon the glass, they become 
aligned along the magnetic lines of force so 


/ ^ " 'v \ 



that the lines are plainly shown. By shifting 
the glass to various positions with relation to 
the magnet, the lines of force forming different 
parts of the field can be shown. 

A compass needle, when placed in a magnetic 
field, always points from the north pole of the 
magnet and to the south pole. For this rea¬ 
son, magnetic lines of force are said to fiow out 
of the north pole, and through the magnetic 
field to the south pole. The total number of 


magnetic lines of force are crowded closely 
together in a strong field, a strong field is 
properly called a dense field. The magnetic 
field is densest around the poles of the magnet. 

When a magnet is broken, each of the pieces 
becomes a magnet. If the pieces are arranged 
in the order shown in Fig. 206, the magnetic 
lines of force fiow in at the end of the piece 
that was the south pole of the magnet and 
from piece to piece toward the end of the 
piece that was the north pole of the magnet. 
From this it is assumed that magnetic lines 
of force not only fiow from the north pole to 
the south pole outside the magnet, but from the 
south pole through the magnet to the north 
pole, and so fiow through complete circuits. 

Characteristics of Magnetic Lines of Force 

1. Continuous—fiow out of the north pole 
of the magnet, from the north pole to the 
south pole outside the magnet, back into the 
magnet at the south pole, and from south to 
north within the magnet. 

2. Lines of force repel each other or spread 
apart. 

3. Lines of force tend to contract or short¬ 
en their path. 

4. Lines of force tend to crowd into and 
fiow through magnetic materials. (See Fig. 
207.) 

5. Lines of force fiow through all materials; 
that is, they cannot be insulated. 

Magnetic Compass 

The earth is a large natural magnet having 
a south magnetic pole near its north geo¬ 
graphical pole and a north magnetic pole near 
its south geographical pole. (See Fig. 208.) 
The compass needle is a small bar magnet 
mounted on a pivot so that it is free to turn. It 
is marked so that its north pole can be easily 
distinguished. Its north pole is attracted by 
the earth’s south magnetic pole and drawn 



these magnetic lines makes up what is called 
the magnetic flux. Fig. 203 shows the con¬ 
ception of a magnetic field set up by a horse¬ 
shoe magnet. 

The stronger the magnetic field the more 
magnetic lines of force are set up and the 
closer they are crowded together. Since the 



toward the north geographical pole, and its 
south pole is attracted by the earth’s north 
magnetic pole and drawn toward the south 
geographical pole. This causes the compass 
needle to align itself with the earth’s mag¬ 
netic lines of force, and therefore point north 
and south. 









































]\I A G N E T I S M 


205 


Molecular Theory of Magnets 

The molecular theory of magnets assumes 
that magnetic materials are composed of mole¬ 
cules which are each a tiny magnet having a 
north pole and a south pole. In the unmag¬ 
netized state these molecules lie with their un¬ 
like poles adjacent so that the magnetic cir¬ 
cuits are complete within the bar. In the mag- 


stronger the magnetic field the stronger the bar 
becomes magnetized. The bar becomes so 
magnetized that its poles are unlike the poles 
of the magnet to which they are adjacent. (See 
Fig. 207.) The attraction between the unlike 
poles of the bar and the magnet, draws or 
tends to draw, the bar and magnet together. 
The attraction between the unlike poles is 


! \ 



FIG. 

netized state these molecules are aligned so 
that the magnetic lines of force must pass out 
of the bar at some point, flow through the 
space surrounding the bar, and back into the 
bar at another point to complete their magnetic 
circuit. Magnetizing a bar, then, is taken as 
aligning its molecules. 

Figs. 209 and 210 respectively show the 
theoretical state of unmagnetized and mag¬ 
netized bars. Fig. 209 shows the molecules 
lying with unlike poles adjacent, completing 



the magnetic circuits within the bar. Fig. 210 
shows a magnet that is magnetized to the 
theoretical saturation point. In practice this 
degree of magnetization is never reached. 

Magnetic Induction 

A bar of iron or steel becomes magnetized 
when placed in a magnetic field. It is said to 
be magnetized by magnetic induction. The 


206 

often described as caused by the magnetic lines 
of force tending to contract or shorten their 
length and so pull one pole to the other. 

Permeability and Retentivity 

Soft iron is much easier to magnetize than 
is hard steel, but soft iron remains magnetized 
only so long as it is under the influence of a 
magnetizing force. Hard steel is more difficult 
to magnetize, but when it is magnetized, it re¬ 
mains magnetized indefinitely. Soft iron is 
said to have high permeability, but, since it 



FIG. 208 

demagnetizes when removed from the magnet¬ 
izing force, it is said to have very low retentiv¬ 
ity. Hard steel, on the other hand, is said to 
have low permeability but high retentivity. 
Permeability expresses the relative ability of 





































20G 


ELEMENTS OF ELECTRICITY 


magnetic materials to be permeated by mag¬ 
netic lines of force. It expresses the relative 
ease with which a magnetic material becomes 
magnetized. The value of permeability is ob¬ 
tained by comparing the number of lines of 
force in a certain area in the material, with the 
number of lines of force in the same area in air, 
under the same conditions. 


aligned they cannot twist out of alignment so 
easily. 

There is a magnetic phenomenon which 
strongly supports the molecular explanation 
for permeability and retentivity. When hard 
steel is rapidly magnetized and demagnetized 
it becomes heated. Rapidly magnetizing 
and demagnetizing soft iron does not pro- 




:m CM CM cm cm cm cm cm cm CM cm cm cm cm CM cm cm CM rm 
CM cm cm cm cm cm cm cm am cm cm cm cm cm cm cm cm cm 

cmcm cm M Mcm cMCMMcm CMMcmcMcmcmcmMcm 
McmcmMcmcmLMcmMcmcMcmcmcmcmMcmcM 
cm cm cm cm cm CM cm MM CM CM LM cm urn cm CBM Mcm 


FIG. 209 


FIG. 210 


Retentivity is the ability of a magnetic ma¬ 
terial to “retain magnetism,” or remain mag¬ 
netized. Soft iron and annealed steel have 
high permeability but practically no retentivi¬ 
ty. Cast iron and hard steel have low permea¬ 
bility, but high retentivity. Hard steel has very 
high retentivity, hence is used for the manu¬ 
facture of permanent magnets. 

The molecular theory of magnets offers a 
simple explanation for the high permeability 
and low retentivity of soft iron, and the low 
permeability and high retentivity of hard 
steel. The explanation assumes that the 
molecules of soft iron can twist with ease 
within the bar, but the molecules of hard 
steel can twist only with difficulty. The mole¬ 
cules of soft iron can readily twist into align¬ 
ment when the soft iron bar is placed in the 
field and so is readily magnetized. But, since 
the molecules twist with ease, they twist 



out of alignment as soon as the soft iron is 
removed from the influence of the magnetic 
force. The molecules of hard steel cannot 
twist so easily, consequently a stronger field 
is required to align them, and when once 


duce so much heat. If magnetizing is aligning 
the molecules and the molecules of soft iron 
twist with ease, it is evident that rapidly mag¬ 
netizing and demagnetizing soft iron will not 
produce as much heat as rapidly magnetizing 
and demagnetizing hard steel. 

Reluctance 

Reluctance is the opposition offered to the 
flow of magnetic lines of force. Materials that 
have high permeability have low reluctance 
and materials that have low permeability 
have high reluctance. Non-magnetic materials 
have about the same reluctance as air. 

Recharging Magnets 

Magnets that have become weak can be re¬ 
magnetized on a magnet charger. The mag¬ 
net charger is a strong electro-magnet. Fig. 
211 shows an electro-magnet that is used for 
recharging magnets. When a magnet is placed 
on a charger, unlike poles of the charger and 
the magnet must be placed together. If like 
poles of the magnet and the charger are placed 
together, the polarity of the magnet will be 



reversed. Once the polarity of a magnet is 
reversed it is seldom possible to remagnetize 
it as strongly as'it would be if the polarity had 
not been reversed. The attraction between the 
charger and the magnet cannot be taken as 
evidence that unlike poles are together, since 
the charger being so much stronger than the 








































M A G N E T I S M—E LEM ENT ARY ELECTRICITY 


207 


magnet, reverses the polarity of the magnet 
easily. If the magnet is suspended high 
enough so that the charger will not reverse its 
(magnet’s) polarity, then a slight repulsion 
can be perceived if like poles are adjacent. 

Care and Assembling of Magnets 

Jars and sharp knocks cause magnets to de¬ 
magnetize. If magnets are permitted to stand 
without keepers across their poles they de¬ 
magnetize. A keeper is a bar of soft iron that 
can be placed across the poles of the magnet 
to form a path of low reluctance for the 


lines of force from one pole to the other. 
(See Fig. 212.) If magnets are placed together 
so that unlike poles are adjacent, one magnet 
acts as a keeper for the other. When unlike 
poles are placed together one magnet attracts 
the other. If magnets are assembled on a mag¬ 
neto, like poles must be placed together. If 
unlike poles of the magnets are placed to¬ 
gether, one magnet so neutralizes the other 
that a strong field can not be set up. When like 
poles are placed together one magnet repels 
the other. 


ELEMENTARY 

Electricity is an agent of energy used to pro¬ 
duce ignition sparks for the engine, to light the 
lamps, to crank the engine when starting, and 
to accomplish various other operations which 
are more or less necessary for the comfort and 
safety of automobile passengers and drivers. 
The exact nature of electricity is unknown, 
and no attempt will be made here to definitely 
explain what it may be. However, the action 
of electricity under certain conditions is defi¬ 
nitely known, and the uses to which it is put 
are many. 

The word “electricity” is derived from 
“elektron,” the Greek word for amber. The 
ancient Greeks discovered that amber, after 
being rubbed to polish it, would then attract 
small bodies, such as chaff, lint, etc. Why the 
polishing of amber caused it to attract small 
bodies, the Greeks made no attempt to explain, 
but attributed it to a mystical property pos¬ 
sessed by amber. Later it was discovered that 
other materials after being rubbed together 
would then attract chaff, lint, bits of paper, 
etc., just as amber. These attractions were 
then named electric attractions (meaning at¬ 
tractions like that of amber) to distinguish 
them from magnetic attractions. 

After hard-rubber has been rubbed with cat’s 
fur, both the hard rubber and the cat’s fur at¬ 
tract small bodies. The hard rubber and the 
cat’s fur also attract each other, but the hard 
rubber will repel another piece of hard 
rubber that has been rubbed with cat’s fur, 
and the cat’s fur will repel other cat’s fur 
that has been rubbed on hard rubber. The 
change in condition of the hard rubber and 
cat’s fur brought about by rubbing one on the 
other, is described by saying they are charged 
with unlike electric charges by the friction of 
one rubbing on the other; and the cause for the 
attraction and repulsion is explained by the 
statement, UNLIKE CHARGES ATTRACT, 
LIKE CHARGES REPEL. There are various 


ELECTRICITY 

other materials such as flint-glass and silk, 
cat’s fur and sealing wax, flannel and ebonite 
that, when rubbed together, behave much in 
the same manner as the hard rubber and the 
cat’s fur. 

When highly electrified bodies carrying un¬ 
like charges are brought near to each other, 
there is usually a spark between the bodies and 
a crackling sound produced. After the spark 
and crackling sound the bodies are found to be 
discharged. The spark thus produced is called 
an electric spark, and is a result of electricity 
passing from one body to the other. The dis¬ 
charging of the bodies is brought about by one 
charge being unlike the other and so one 
neutralizes the other. Bodies which can be 
discharged by sparking through greater dis¬ 
tances are said to be charged to higher po¬ 
tentials. 

Electric charges produced by friction of one 
material rubbing on another are called friction¬ 
al electricity, or static charges. They are call¬ 
ed static charges because they seem to be held 
at rest on the bodies. Static electricity is of 
little importance since the amount of elec¬ 
tricity moving from one body to another when 
a discharge takes place, is too small to be of a 
practical use. However static electricity is 
one source of trouble which has only recently 
come to light. The flow of gasoline, either 
through a hose or through a metal retainer, 
such as a funnel, generates static charges 
which produce electric sparks when the air 
is very dry, as in a heated garage in winter. 
However, the spark cannot be produced if there 
is metal-to-metal contact at all points. There¬ 
fore it is well to see that the filling can or hose 
has metal contact with the funnel and that the 
funnel has metal contact with the gasoline 
tank. 

Since the nature of electricity is not defi¬ 
nitely known we can merely speculate as to 
what it is. Electricity acts as if it were a 



208 


ELEMENTS OF ELECTRICITY 


weightless, invisible, non-compressible fluid 
permeating all space—saturating everything. 
The fact that electricity is not a fluid is defi¬ 
nitely known; but, since the laws governing the 
flow of fluids through a pipe are much the 
same as the laws governing the flow of elec¬ 
tricity through a circuit, it is to our advantage, 
for the purpose of explanation, to think of it as 
acting like the imaginary special kind of fluid 
described above. 

CONDUCTORS AND INSULATORS 

There is no material which cannot be 
charged with electricity, but electricity moves 
through some materials with greater ease than 
through others. Materials which will conduct 
an electric current are called conductors. 
There is no material that does not offer some 
resistance to the flow of electricity, and so 
there is no perfect conductor. Some materials 
are much better conductors than others. All 
metals are good conductors. Some materials 
offer such high resistance to the movement of 
electricity that it is practically impossible to 
pass electric currents through them. These 
materials which offer very high resistance to 
the movement of electricity are called insula¬ 
tors. Some materials are much better insula¬ 
tors than others, but there are no materials 
through which electricity cannot be moved to 
Isome extent and for this reason we have no 
perfect insulator. 

The following is a list of materials classed 
as good conductors, fair conductors, partial 
conductors, and insulators. Silver, the best 
conductor, is placed first. The better insula¬ 
tors are placed last. 

Good Conductors: 

Silver 

Copper 

Aluminum 

Zinc 

Brass 

Platinum 

Iron 

Lead 

Mercury 

Fair Conductors: 

Carbon 

Acid solutions (electrolytes) 

Living vegetable substances 
Moist earth 

Partial Conductors: 

Water 

Animal bodies 
Linen and cotton 
Dry wood 
Marble 


Non-Conductors (Insulators): 


Slate 

Resin 

Oils 

Rubber 

Porcelain 

Shellac 

Dry leather 

Mica 

Dry paper 

Paraffin 

Wool 

Glass 

Silk 

Air 


POSITIVE AND NEGATIVE CHARGES 

The unlike electric charges have been named 
“Positive” and “Negative.” The positive 
charge is taken as one of higher electrical 
pressure. A positive charge may be thought 
of as an excess of electricity; that is, more 
than the normal amount of electricity being 
present. We may think of electricity forming 
a positive charge in much the same manner as 
air compressed in a tank. Electricity forming 
a positive charge, like air compressed in a tank, 
tends to escape from the body in which it is 
confined. The negative charge is taken as one 
of lower electrical pressure. We may think of 
a negative charge as being a partial “electrical 
vacuum;” that is, a condition in which less than 
the normal amount of electricity is present. 
Bodies in this condition tend to draw electricity 
toward them. Bodies carrying unlike charges 
are bodies charged to unequal electrical pres¬ 
sures. 

ELECTROMOTIVE FORCE 

When bodies charged to unequal electrical 
pressures are connected by some material 
through which electricity will flow, electricity 
moves or flows through the conductor from the 
body of higher electrical pressure to the body 
of lower electrical pressure, until the pressure 
becomes the same on both bodies. Electricity 
moving through the conductor is an electric 
current. The force that moves electricity 
from one point to another is called Elec¬ 
tromotive Force, or “electric moving force.” It 
is usually abbreviated E. M. F. Electromotive 
Force is the attraction of unlike charges. 

ELECTRIC CIRCUIT 

The electric circuit is a path that an elec¬ 
tric current follows. To form an electric cir¬ 
cuit the path must be complete and made of 
materials which are conductors. The conduc¬ 
tors are usually covered with some insulating 
material to prevent them from touching, should 
two of them come together. 

To have an electric current, it is necessary to 
have a complete circuit and an electromotive 
force. The electromotive force is usually sup¬ 
plied by either generators, or batteries. A gen¬ 
erator, or battery, forces the electricity from 
one point to another. Forcing electricity from 
one point to another creates points of unequal 



ELEMENTARY ELECTRICITY 


209 


electrical pressure, and so produces the electro¬ 
motive force. 

Fig. 214 illustrates a simple electric circuit. 
The electromotive force is supplied in this cir¬ 
cuit by a generator. The lamps are connected 
to the generator by copper wires, which are 
represented by heavy lines. The generator, 
when running, forces electricity through the 
lamps. 

The hydraulic circuit in Fig. 213 is analo¬ 
gous to the electric circuit in Fig. 214. The 
centrifugal pump, pipes, and pipe coil corre¬ 
spond respectively to the generator, wires, and 
lamps. The pipes and pump are assumed 
to be filled with water. When the pump is 
driven, it draws the water out of the lower pipe 
and crowds it into the upper pipe. This re¬ 
sults in a difference in pressure being produced 


•which the water is pumped through the cir¬ 
cuit. This meter corresponds to the ammeter 
(A) in the electric circuit. 

Strength of Current 

The rate water flows through the hydraulic 
circuit depends upon the force produced by the 
pump and the resistance offered to the flow of 
the water through the pipes. This resistance 
depends upon the length of the pipes and their 
size. Likewise in the electric circuit the rate 
the electricity flows through the electric circuit 
depends upon the electrical pressure produced 
by the generator, and the resistance offered by 
the wires and the lamps to the flow of elec¬ 
tricity. 

Figs. 215 and 216 show two simple electric 
circuits, each made up of a generator, a long 




between the pipes. This difference in pressure 
in the hydraulic circuit corresponds to the dif¬ 
ference in electrical pressure produced in the 
electric circuit by the generator. The higher 
pressure in the upper pipe causes the water to 
flow through the pipe coil from the upper pipe 
to the lower pipe. The water flowing through 
the hydraulic circuit corresponds to the elec¬ 
tricity flowing through the electric circuit. The 
meter (P. M.) connected between the pipes 
measures the difference between the pressures 
in the two pipes. This meter corresponds to 
the voltmeter (V) in the electric circuit. Fig. 
214. The meter (C. M.) in the upper pipe of 
the hydraulic circuit measures the rate at 


wire connected to one terminal of the generator 
and to one terminal of an ammeter, the other 
terminal of ammeter connecting to the other 
terminal of the generator. A voltmeter in each 
figure is connected across the terminals of the 
generator. The voltmeter measures the elec¬ 
tromotive force produced by the generator, and 
the ammeter measures the rate that the elec¬ 
tricity is forced through the circuit. 

In Fig. 215 the wire is a No. 10 copper wire, 
500 ft. long. When the generator is driven fast 
enough for a voltmeter to read “5,” the am¬ 
meter will then read “10.” If the generator is 
driven fast enough to make the voltmeter read 
“10,” the ammeter will then read “20.” Thus 













































210 


ELEMENTARY ELECTRICITY 


it is, when the resistance of the circuit is kept 
the same, and the E. M. F. is doubled, the 
strength of the current will be doubled. 

In Fig. 216 the wire is a No. 10 copper wire, 
250 ft. long. The wire in the circuit in Fig. 
216 is half as long as the wire in the circuit in 
Fig. 215, hence the resistance of the circuit in 
Fig. 216 is about half the resistance of the 
circuit in Fig. 215. When the generator in the 
circuit in Fig. 216 is driven fast enough for the 
voltmeter to read “5,” the ammeter then reads 
“20.” Thus it is, when the resistance of the 
circuit is reduced one-half and E. M. F. kept the 
same, the strength of the current is doubled. 
The facts brought out by the consideration 
of the two figures are stated in a law called 
“Ohm’s Law.” Ohm’s law is as follows: 

OHM’S LAW 

The strength of the current is directly pro¬ 
portional to the E. M. F. and inversely propor¬ 
tional to the resistance. 

Ohm’s law, though simple, is very important 
and must be remembered. 

Before attempting to measure electromotive 


OHM 

The ohm is the unit of resistance. A No. 10 
copper wire, one thousand feet long, has a re¬ 
sistance of approximately one ohm. The re¬ 
sistance of a conductor can be calculated by 
the joint use of a voltmeter and an ammeter. 

The volt, ampere and ohm have been select¬ 
ed of such values that one volt causes a current 
of one ampere to fiow through a resistance of 
one ohm. 

By Ohm’s law. 

Volts divided by Ohms equal Amperes. 

Volts divided by Amperes equal Ohms. 

or Amperes multiplied by Ohms equal 

Volts. 

Where, 

E represents volts, or electromotive force. 

I represents amperes, or strength of cur¬ 
rent. 

R represents ohms, or resistance. 

Then, 

E F 

^=I IR = E 



force, strength of current, or resistance, it is 
necessary to become familiar with the units 
used. 

VOLT 

The unit of electromotive force is the volt 
and wherever used it should bring to mind the 
thought of “electrical moving force” or pres¬ 
sure. The instrument used to measure it is 
called a voltmeter. An ordinary dry-cell gives 
an E. M. F. of about one and one-half volts. A 
lead plate storage cell gives an E. M. F. of 
about two volts. 

AMPERE 

The unit for measuring the strength of an 
electric current is the ampere, and the instru¬ 
ment used to measure it is called an ammeter. 


With the above formulas the resistance can 
be calculated when the volts and amperes are 
known, by dividing the number of volts by the 
number of amperes. If the volts and ohms 
are known, the amperes can be found by di¬ 
viding the number of volts by the number of 
ohms. If the amperes and ohms are known, 
the volts can be found by multiplying the num¬ 
ber of amperes by the number of ohms. These 
formulas are of great value in estimating the 
result without having to make actual test. 

TYPES OF CIRCUITS 

There are two principal ways of connecting 
electrical appliances; namely. Series and Par¬ 
allel. 






























ELEMENTARY ELECTRICITY 


211 


Series Circuit 

Electrical appliances are said to be con¬ 
nected in series when they form one continuous 
path and the current which flows through one 
must flow through the others. (See Fig. 217.) 
The total resistance of appliances connected 
in series is equal to the sum of their separate 
resistances. The total resistance of the lamps 
in Fig. 217 is six ohms. 

Voltage Drop—IR Drop 

When appliances are connected in series, the 
strength of the current in any one is the same 
as that in any one of the others, but the voltage 
acting on each appliance is proportional to the 
resistance of the appliance. 

The drop or the difference in electrical pres¬ 
sure as a circuit is followed around from the 
positive terminal to the negative terminal of 
the source of E. M. F., or vice versa, is called 
“Voltage Drop,” or “IR” drop. The voltage 


by taking the reciprocal of the sum of their 
reciprocals. (The reciprocal of a number is 1 
divided by the number. Example—The recip¬ 
rocal of 2 is 1/2. The reciprocal of 4 is 1/4. The 
reciprocal of a fraction is equal to the fraction 
inverted; thus, the reciprocal of 1/2 is 2/1, of 
2/3 is 3/2, etc.) 

Fig. 218 illustrates three lamps connected in 
parallel and in circuit with a six-volt battery. 
With this connection, each lamp forms a sep¬ 
arate path for the current to take from the 
positive wire to the negative wire. The full 
voltage of the battery acts on each lamp. The 
strength of the current through each lamp is 
three amperes. [6, (No. of volts) 2, (No. of 
ohms) = 3, (No. of amperes).] Since the cur¬ 
rent flows through each lamp at the rate of 
three amperes, the battery must force the cur¬ 
rent from the negative wire to the positive wire 
at the rate of nine amperes. The joint re¬ 
sistance of these three lamps in parallel is two- 
thirds of an ohm. [2, (ohms resistance in one 



drop across any part of an electric circuit is 
equal to its resistance in ohms, multiplied by 
the number of amperes passing through it. If 
the resistance, and the strength of the current 
are not known, a voltmeter must be used to 
determine the voltage drop. 

Parallel or Multiple Circuit 

Electrical appliances are connected in par¬ 
allel when each forms a separate path for the 
current to take from one point to another. 
When appliances are connected in parallel, the 
voltage acting on one is equal to the voltage 
acting on any other one. The strength of the 
current passing through each of the appliances 
connected in parallel is inversely proportional 
to its resistance. The joint resistance of 
appliances in parallel is always less than the 
resistance of any one of the appliances. If the 
appliances have equal resistances, their joint 
resistance can be found by dividing the 
resistance of one by the number connected in 
parallel. If the appliances have unequal resist¬ 
ances their joint resistance may be found 


lamp) -f- 3, (number of lamps in parallel) = 
2/3 (No. of ohms joint resistance).] 

Consider now the lamps in Fig. 218 as hav¬ 
ing one ohm, two ohms, and three ohms re¬ 
sistance respectively. Six amperes then flows 
through the first lamp, three amperes through 
the second, and two amperes through the third. 
The battery now forces the current through 
the circuit at the rate of eleven amperes. Since 
eleven amperes flow under six volts pressure, 
the joint resistance of the circuits must be six- 
elevenths ohms. [6, (No. of volts) ^ 11, (No. 
of amperes) = 6/11, (No. of ohms).] The 
joint resistance of the lamps may be found in 
this manner, or by taking the reciprocal of the 
sum of their reciprocals. The following is an 
example, to illustrate how to take the recip¬ 
rocal of the sum of the reciprocals of numbers. 

1/1 (reciprocal of “1”) + 1/2 (reciprocal of 
“2”) 4- 1/3 (reciprocal of “3”) =6/6 -f 3/6 
+ 2/6 = 11/6 (the sum of their reciprocals). 

1 -y-11/6 (reciprocal of the sum of their recip¬ 
rocals) = 1x6/11 == 6/11, No. of ohms joint 
resistance. 























212 


ELEMENTARY ELECTRICITY 


There is usually little difficulty in calculating 
the joint resistance of appliances in series, 
since the combined resistance increases as the 
number of appliances in series increases. On 
the other hand, calculating the joint resistance 
of appliances in parallel is usually found con¬ 
fusing at first. The difficulty arises chiefly 
from the fact that the meaning of the term, 
joint resistance, is not understood. Joint re¬ 
sistance is the resistance of that part of the 
circuit which the appliances jointly form. 
Since more paths are provided for the current 
to take, the joint resistance of appliances in 
parallel always decreases as the number in 
parallel increases. 

ELECTRICAL POWER—WATT 

The watt is a unit of electrical power. Work 


tional to its cross-sectional area. The longer 
the conductor the higher its resistance; the 
larger the conductor the lower its resistance. 
If the length of the conductor is doubled its re¬ 
sistance is doubled; if the length is reduced 
one-half its resistance is reduced one-half. If 
the cross-sectional area of the conductor is 
doubled the resistance is reduced one-half; if 
the cross-sectional area of the conductor is re¬ 
duced to one-half its resistance is doubled. 

The resistance of a conductor depends large¬ 
ly upon the kind of material used. Silver is the 
best conductor, hence has the lowest resist¬ 
ance. Copper is a very good conductor but has 
slightly higher resistance than silver. The fol¬ 
lowing is a table giving the relative resistance 
of the more common metals, as compared to 
the resistance of copper. 



is being done at the rate of one watt when 
one ampere fiows under an E. M. F. of one volt. 
Watts are equal to the volts multiplied by the 
amperes. 

Where, 

P represents watts, or power 

Then, 

P P 

EI = P ^ = I ^ = E 

E I 

An electrical horse-power equals 746 watts. 

A kilowatt is one thousand watts. 

A watt-hour is one watt acting for one hour. 
Watt-hours are equal to the watts multiplied 
by the hours. A kilowatt-hour is one thou¬ 
sand watt-hours. 

RESISTANCE 

Resistance, as an electrical term, is the oppo¬ 
sition offered by a material to the fiow of elec¬ 
tricity. The resistance of a conductor depends 
upon (a), length, (b), cross-sectional area, 
(c), material used for conductor, and (d), tem¬ 
perature. 

The resistance of a conductor is directly pro¬ 
portional to its length and inversely propor- 



Ohms Per 

Relative 

Resistance 

Conductor 

Circular 

as Compared 


Mil Foot 

to Copper 

Silver, pure annealed. 

. . 9.7 

0.925 

Copper, annealed . 

. .10.5 

1.000 

Copper, hard-drawn . . . . , 

. .10.8 

1.022 

Aluminum (97.5 per cent 
pure) . 

. .17.7 

1.672 

Zinc (very pure). 

. .38. 

3.608 

Iron wire . 

. .65.2 

6.173 

Nickel . 

. .85. 

7.726 

Steel wire. 

. .90. 

8.621 

Brass . 


4.515 

Phosphor-bronze . 


5.319 

German Silver. 

.128.29 

17.300 


The resistance of all pure metals increases 
with an increase in temperature. Copper in¬ 
creases about twenty-two hundredths of one 
per cent (.0022) in resistance for each degree 
Fahrenheit increase in temperature. The re¬ 
sistance of certain alloys does not increase 
with an increase in temperature. For example, 
Manganin, an alloy of 84 parts copper, 12 parts 
nickel, and 4 parts manganese, all by weight, 
has a negligible temperature change for prac¬ 
tical purposes. Other alloys having similar 




























ELEMENTARY ELECTRICITY 


213 


properties are produced. The resistance of 
most alloys increases with an increase in their 
temperatures, but to a less degree than do the 
resistance of pure metals. 

Brown & Sharpe Wire Gauge 

Wire gauges are arbitrary standards for the 
measurement of the sizes of wire. The Brown 
& Sharpe gauge, which is the same as the 
American Wire Gauge, is the standard in the 
United States for the measurement of copper 
wires. Wire sizes are referred to as gauge num¬ 
bers, and usually the smaller the number, the 
larger the wire. Every third number from any 
given number of the Brown & Sharpe gauge 
gives a wire size with either approximately half 
the area or twice the area. To illustrate—a 
No. 10 wire is approximately twice the area of 
a No. 13 wire, and approximately half the area 
of a No. 7 wire. 


foot. The resistance of a circular mil foot of 
ordinary commercial grade copper wire at a 
temperature of 75° F. is about 10.8 ohms. The 
resistance of a copper wire can be found by 
multiplying the length in feet by 10.8 and di¬ 
viding by the diameter of the wire in mils 
squared. By formula, resistance in ohms can 
be found as follows:. 

^ Length in feet x Ohms per Cir. M. Ft. 

JK. "" . - . I , I 

Sectional area in Cir. Mils. 

The resistance of copper wire varies with the 
degree of purity of the copper used and so the 
resistance for various lengths of wire as given 
in the wire table can be taken only as approxi¬ 
mate, unless the degree of purity is expressed. 
The resistances given in the following wire 
table are for wires of standard grade and at a 
temperature of 68 degrees F. Unless a high 
degree of accuracy is necessary, the resist- 



CIRCULAR MIL 

The size of a wire is proportional to its cross- 
sectiofial area. Computing the area of a circle 
by the common square units involves fractions 
that are more or less complex. Hence, a unit 
called the Circular Mil is used for measuring 
the cross-sectional area of wire. A circular 
mill is the area of a circle one thousandth 
(.001") of an inch in diameter. The area of 
circles vary as the squares of their diameters. 
That is, the area of a circle of a diameter 
of .002" (two mils) is four times the area 
of a circle of a diameter of .001" (one mil). 
It follows that since a circle of a diameter 
of .001" is one circular mil and a circle of a 
diameter of .002" has four times the area of 
the circle .001" in diameter, the area of the 
circle .002" in diameter is 4 circular mils. The 
cross-sectional area of any conductor in circu¬ 
lar mils is equal to the diameter of the con¬ 
ductor in mils, squared. 

CIRCULAR MIL FOOT 

A circular mil foot is the unit conductor, A 
wire having a sectional area of one circular 
mil, and a length of one foot is a circular mil 


ances as given in the table can be taken for 
copper wire of the various sizes and lengths. 

STANDARD COPPER WIRE TABLE 

Weights, lengths and resistances of wire 
at 68° F. 

Safe Carrying 


A.W.G. 

Dla. 

Area 

I.ength 


Capacity 



# 




Insulat'ns 



Circular 

Feet 

Feet 

Rubber 

Other 

K.&S. 

Indies 

Mils 

Per I.b. 

Per Ohm 

Insula¬ 

Tlian 






tion 

Rubber 

000 

.4096 

167,800 

1.968 

16,180 

175 

275 

1 

.2893 

83,690 

3.947 

8,070 

100 

150 

4 

.2043 

41,740 

7.914 

4,025 

70 

90 

7 

.1443 

20,820 

15.87 

2,007 

43 

56 

10 

.1019 

10,380 

31.82 

1,001 

25 

30 

14 

.06408 

4,107 

80.44 

396 

15 

20 

18 

.04030 

1,624 

203.4 

156.6 

3 

5 

20 

.03196 

1,022 

323.4 

98.5 



22 

.02535 

642.4 

514.2 

61.95 



32 

.007950 

63.21 

5,227 

6.095 



36 

.0050 

25.0 

13,210 

2.411 



38 

.003965 

15.72 

21,010 

1.516 



40 

.003145 

9.888 

33,410 

.9534 




SIMPLE ELECTRIC CELLS 

If two unlike materials are immersed in some 
chemical solution that attacks one of the 
metals only, or one more than the other, they 
will become charged to unequal electrical pres¬ 
sures. The difference in electrical pressures 
on the metals depends upon the kind of metals, 
and upon the strength and kind of solution. 























214 


ELEMENTS OF ELECTRICITY 


Two metals, such as copper and zinc, im¬ 
mersed in a solution of sulphuric acid form a 
simple electric cell. When the zinc and copper 
are placed in the acid, a chemical action im¬ 
mediately begins. The sulphur and oxygen 
elements of the acid attack the zinc, forming 
zinc sulphate, and liberate (or set free) the 
hydrogen element as shown by bubbles rising 
to the top of the liquid and also forming on the 
surface of the copper. As this chemical change 
takes place, the copper plate becomes charged 
to a pressure of about one volt above that of 
the zinc. 

If a wire connects the top of the copper plate 
to the top of the zinc plate, an electric current 
will pass through the wire from the copper to 
the zinc. As long as the current flows from 
the copper plate to the zinc plate, the chemical 
action continues between the acid and the 
zinc. If the wire is disconnected, and the cop- 


solution. The larger the plates, and the more 
solution, the higher the ampere capacity of the 
cell. The voltage of the cell does not depend 
upon the size of the plates, but upon the kind 
of metals used in the plates and the solution. 

Discharge 

The chemical action in the cell which forces 
the electricity through a circuit will continue 
until the zinc has been entirely eaten away or 
the acid has been exhausted. When the zinc 
has been entirely eaten away the cell is dis¬ 
charged and will no longer force current 
through a circuit. Just as the maximum 
rate at which the cell will force current 
through a circuit depends upon the size of 
the plates, so does the life of the cell depend 
upon the amount of zinc, or the size of the zinc 
plate. The thicker and heavier the zinc plate 
the longer the life of the cell. A pound of zinc 



’ SERIES-PARALLEL CONNECTIONS. 
FIG. 219 


per and zinc are pure, the chemical action prac¬ 
tically stops. 

The rate at which the chemical action 
takes place between the zinc and acid has a 
direct relation to the rate electricity flows 
through the wire from the copper plate to the 
zinc plate. 

There is, however, a limit to the rate at which 
the chemical action will take place and so 
there is a limit to the rate at which the cell 
will force the current through the wire. The 
rate the cell will force the current through the 
wire is the ampere capacity of the cell. The 
capacity of the cell depends upon the size of 
the plates and the volume and strength of the 


for the zinc plate will give about 370 ampere- 
hours; that is, a pound of zinc will be sufficient 
for the plate of a cell that will keep one am¬ 
pere flowing for 370 hours. 

Polarization 

The hydrogen gas which collects around the 
copper plate while the cell is discharging, is 
likely to cling to it and in time almost com¬ 
pletely cover the part immersed in the solution. 
Hydrogen gas offers a high resistance to the 
flow of current and so insulates the copper 
plate from the solution, thus retarding the 
chemical action, and adding to the conditions 
which make up an internal resistance in the 



























E L E :\I E X T A R Y ELECTRICITY 


215 


cell. When this condition is reached, the cell 
is said to be polarized. If polarization is not 
counteracted in some way the cell is of no 
practical use. 

Local Action 

All commercial zinc contains particles of car¬ 
bon, iron and various other metallic impurities, 
which cause a chemical action to take place 
between the acid and the zinc when the copper 
plate is not connected to the zinc. The zinc 
together with some metallic impurity, such as 
a particle of carbon, and the solution form a 
simple cell. The chemical action between the 
acid and the zinc, charges the carbon to a 
higher pressure than the zinc, but since the 
carbon and zinc are in contact, electricity 
passes from the carbon back to the zinc, so 
that the unlike charges cannot build up high 
enough to stop the chemical action. As a re¬ 
sult, the zinc is continuously being eaten away 
and the cell discharges without forcing the 
current through a circuit where it can be made 


7 ^VOLTS 



to do work. This is called local action. It can 
be prevented by using chemically pure zinc, or 
by amalgamating the zinc. This is accom¬ 
plished by wetting it with the acid, and then 
rubbing its surface with mercury. 

Dry Cell 

A dry cell is an electric cell, the action of 
which is much like that just described. The 
dry cell is not truly a “dry” cell, but is so called 
since there is no liquid to spill. However if 


a dry cell is completely dried out, it is useless. 
The principal parts of a dry-cell are as follows: 

A zinc cylinder or can is used for the nega¬ 
tive plate. Inside of this zinc cylinder several 
layers of thick blotting paper are placed which 
are saturated with a solution of sal-ammoniac 
and zinc chloride. Inside of this is placed a 
carbon rod, which acts as the positive plate. A 
mixture of sawdust, charcoal, carbon granules 
and manganese peroxide is packed between 
the carbon rod and the blotting paper. The blot¬ 
ting paper extends only within about an 
inch of the top of the zinc, and the carbon 
rod is long enough to extend out above the top 
of the mixture. Over the top of the mixture 
is placed heavy corrugated paper or fine sand. 
Over this is poured a melted pitch sealing 
compound which cools and seals the blot¬ 
ting paper, mixture, and carbon rod in the 
zinc can. Terminals are provided for connec¬ 
tions to the zinc and to the carbon. The chemi¬ 
cal action, which takes place on the zinc. 


7A VOLTS 



causes the carbon rod to become charged to 
electrical pressure of about one and one-half 
volts higher than that of the zinc. As a cell 
discharges, there is a tendency towards polar¬ 
ization. The manganese peroxide is added so 
that oxygen from it will combine with the 
hydrogen as it forms, and reduce polarization. 
The corrugated paper, or fine sand at the top 
of the cell, provides an expansion chamber 
^ which permits the contents of the cell to ex- 
' pand with an increase in temperature without 














216 


ELEMENTS OF ELECTRICITY 


cracking the pitch seal. A cardboard case 
acts as a protection and insulation for the 
zinc. 

Voltage of Dry Cell 

The electromotive force produced by a dry¬ 
cell when new is about one and one-half volts. 
This is called its terminal voltage. The ter¬ 
minal voltage drops when the cell is placed on 
discharge. For average working conditions of 
the cell it is about one volt. The drop in ter¬ 
minal voltage is due largely to partial polari¬ 
zation, which takes place as soon as the cell 
is placed on discharge. 

Ampere Capacity 

The short-circuit ampere capacity of a good 
new dry cell varies from 20 to 30 amperes. The 
short-circuit should be made by connecting the 
cell to an ammeter having not more than one- 
hundredth of an ohm resistance. 

Ampere Hour Capacity 

The ampere-hour capacity of dry-cells 
ranges from five to twenty-five ampere hours, 
depending upon the quality of materials used, 
age of cell and manner in which it is discharg¬ 
ed. If a dry-cell is discharged intermittently, 
and at low rate, its ampere-hour capacity is 
much higher than when discharged either con¬ 
tinuously or at higher rates. 

Electric Battery 

The E. M. F. of a cell or the capacity of a 
cell is seldom high enough for the cell to be 
used alone. For this reason several cells are 
usually connected together to produce a high¬ 
er E. M. F. than one cell, or give a higher 
capacity than that of one cell. Two or more 
cells connected in series, parallel, or series- 
parallel form a battery. 

Cells in Series 

Cells are connected in series when the posi¬ 
tive terminal of each connects to the negative 
terminal of the next, as is shown in the upper 
left Fig. 219. When cells are connected in 
series, their combined voltage is equal to the 
sum of their, separate voltages. The current 
capacity of cells in series is equal to the cur¬ 
rent capacity of one cell, since all the current 
must pass through each cell and the internal 
resistances of the cells must be added together. 

Cells in Parallel 

Cells are connected in parallel when the 
positive teminals of all the cells connect to one 
wire and the negative terminals connect to an¬ 
other wire. Cells are connected in parallel to 
prolong their life. The total voltage of cells 
in parallel is equal to that of one cell and 


their total current capacity is equal to the 
sum of their separate current capacities. The 
upper right illustration of Fig. 219 shows cells 
connected in parallel. 

Cells in Series-Pzurallel 

Cells are connected in series-parallel to form 
a battery having a combined voltage and a 
combined current capacity higher than that of 
one cell. The illustrations in the lower left 
and the lower right of Fig. 219 show cells 
connected in series-parallel. The total voltage 
of cells in a series-parallel connection is equal 
to the voltage of a single series of cells. 
The current capacity of cells in a series-parallel 
connection is equal to the sum of the current 
capacities of the series groups. 

The scheme of connection used for a certain 
purpose depends upon the nature of the ap¬ 
paratus to be operated and upon the demands 
for energy. Every electrical appliance is design¬ 
ed to operate under a given electrical pressure 
and will not operate satisfactorily under any 
other pressure. The pressure required to oper¬ 
ate an appliance is predetermined by the man¬ 
ufacturers. 

Application of a dry battery is illustrated in 
Fig. 220. The illustration at the left shows a 
series connection of five dry cells, with a coil 
of wire having 3^,4 ohms resistance connected 
across the terminals of the battery. Under 
these conditions the flow of current is at a 
rate of 2 amperes. The cells which form the 
battery are all discharging at a rate of 2 am¬ 
peres, as they are in series and the total cur¬ 
rent flows through each of them. 

The illustration at the right shows a bat¬ 
tery of 10 cells connected in series-parallel. 
The battery consists of two groups of cells in 
series, having five cells in each series. The 
same coil is connected across the terminals 
of this battery as was used in the illustration 
at the left. In this case, the voltage is just 
the same as if a single series of five cells were 
used, but the ability of the battery to deliver 
current is twice as great. The pressure being 
only 71/2 volts and the resistance of the ex¬ 
ternal circuit being constant, the flow of cur¬ 
rent is the same as in the illustration at left; 
that is, 2 amperes. In this case the current 
is taken from two series of cells instead of 
one, and requires that each group of series 
cells must deliver only one-half of the total 
current, which is one ampere. 

The advantages obtained by employing the 
series-parallel connection of cells are: The 
ability of the battery to deliver current is mul¬ 
tiplied by the number of series groups of cells 
which are connected in parallel, and the cells 
are discharged at a lower rate which results in 
the life of the cells being prolonged. 



STORAGE BATTERIES 


217 


An example of the increase in the life of 
cells by employing a number of series groups 
in parallel can be obtained by comparing the 
batteries shown in Fig. 220. If the rate of dis¬ 
charge in the illustration at left is 2 amperes 
and the life of the cells is 5 hours, the life 


of the cells in the series-parallel connection at 
right is approximately 15 hours, thus by the 
latter arrangement the first cost of the cells is 
only double, whereas their life is 3 times 
greater. 


STORAGE BATTERIES 


A storage battery is a device for storing 
chemical energy. The storage battery does not 
store electricity, as is commonly supposed, but 
instead, it converts the electrical energy in the 
electric current forced through it, into chemi¬ 
cal energy, and stores the chemical energy. 
The chemical energy stored in a battery is 
capable of forcing current back through the 
circuit. 

The storage batteries used for starting and 
lighting purposes on the automobile are all 
of the lead plate type. The plates for these 



FIG. 221 


peroxide of lead, and the lead oxide that is to 
become the active material for the negative 
plates is changed to pure spongy lead. The 
positive plates are brown and the negative 
plates are gray. 

Electrolyte 

The solution in which the plates are im¬ 
mersed is called the electrolyte. The elec¬ 
trolyte is a solution of sulphuric acid (H 2 SO 4 ). 
The specific gravity of the electrolyte for a 
fully charged storage cell should be from 1.275 



FIG. 222 


batteries are pasted; that is, the active 
materials are pasted into framework called 
grids. The grids are cast of an alloy of lead 
and antimony. The materials that become the 
active materials are lead oxides when pasted 
into the grids. After the lead oxides which 
have been pasted into the grids have dried, the 
plates are placed in forming tanks where the 
lead oxide, which is to become the active 
material for the positive plates is changed to 


to 1.300 in temperate latitudes, and from 1.200 
to 1.230 in tropical latitudes. 

Jars 

The jars are usually made of rubber, though 
those in batteries used with farm lighting 
plants or other places where they will not be 
subject to shocks and vibrations, are made of 
glass. In the bottoms of the rubber jars are 
high ribs that support the plates. These ribs 













































































218 


ELEMENTS OF ELECTRICITY 


hold the plates high enough above the bottom 
of the jars so that the sediment which forms in 
the bottom due to the plates shedding does 
not short circuit the cell. 

Separators 

Separators are insulators placed between the 
plates to prevent positive and negative plates 
from touching, which would result in short cir¬ 
cuiting the cell internally. They are usually 
made of wood, though sometimes rubber is 
used. The wood is treated chemically to re¬ 
move any substance which would cause 
trouble when added to a cell. The separators 
are grooved on the side placed next to the posi¬ 
tive plates, because positive plates shed more 
than negative plates. 

Positive Group 

Two or more positive plates secured to a 
strap form a positive group, (See Fig. 222.) A 
lead post is burned to the strap. This post 
forms the positive terminal of the cell in which 
this group is used. 

Negative Group 

Two or more negative .plates, secured to a 
strap form a negative group. (See Fig. 221.) 
The post burned to the strap of this group 
forms the negative terminal for the cell in 
which this group is used. 

Element 

A positive group and a negative group, as¬ 
sembled with separators between the plates 
form an element. There is always one more 
plate in a negative group than in a posi¬ 
tive group of an element, because the posi¬ 
tive plates are more active. 

Cell 

An element sealed in a jar with electrolyte 
forms a cell. An opening is provided in the 
cover plate, so that distilled water may be add¬ 
ed as the water evaporates from the solution. 
If water is not added at regular intervals the 
electrolyte will get below the top of the plates, 
and the capacity of the cell will be reduced. 
The small vents in the caps are to permit the 
gas that forms in the cell to escape. These 
small vents must be kept open. The vent caps 
must be kept on the openings in the covers of 
the cells to keep dirt out. Dirt must be kept out 
of the cells, as some materials cause the cells to 
self-discharge in a short time, while others 
cause chemical actions to take place that dam¬ 
age the plates and separators. The voltage of 
a lead-plate storage cell is from 2 to 2.2 volts 
when charged, and about 1.8 volts when a cell 
is considered discharged. 


Battery 

Two or more cells connected in series, par¬ 
allel or parallel-series, form a battery. The 
voltage of a storage battery depends upon the 
number of cells in series, and the condition of 
the cells. The voltage is approximately two 
times the number of cells in series. 

The ampere hour capacity of a storage bat¬ 
tery depends upon the size and number of 
plates in each cell, the volume and strength of 
the electrolyte, and the condition of the cells. 

The cells of a storage battery to be used on 
an automobile are arranged in a substantial 
wooden box, thoroughly coated with acid-proof 
paint, and provided with suitable handles for 
carrying the battery, and also for anchoring it 
in position in the car. The cells of the bat¬ 
tery are connected together by heavy lead con¬ 
nectors, which are burned to the posts on the 
strap of each group. 

Specific Gravity 

Specific Gravity is the ratio between the 
weight of a substance and the weight of an 
equal volume of water. The Specific Gravity 
of a substance may be found by dividing the 
weight of a volume of the substance by the 
weight of an equal volume of water. The 
specific gravity of battery acid (chemically 
pure sulphuric acid) is 1,835. That is to say, 
a gallon of sulphuric acid weighs 1.835 times 
as much as a gallon of water. The electrolyte is 
part water, therefore, its specific gravity is not 
as high as that of the pure acid. Since the 
specific gravity varies with the percentage of 
acid, it can be used as an accurate measure 
for the strength of the electrolyte. The specific 
gravity of the electrolyte is usually measured 
with an instrument called a hydrometer. 

Hydrometer 

The hydrometer shown in Fig. 223 is a small 
closed glass tube with a small quantity of shot 
sealed in one end, which serves to keep the 
tube in an upright position when it is placed 
in the liquid, and provided with a suitable scale 
marked on the glass tube, or on a piece of 
paper on the inside of the tube. The depth to 
which the hydrometer sinks in the liquid, 
as indicated on the scale of the instrument 
where the surface of the liquid is in contact 
with the tube, is a measure of the specific grav¬ 
ity of the liquid. For convenience in using a 
hydrometer, it is usually placed within a larger 
glass tube provided with a rubber bulb at one 
end, and a suitable nozzle or a short piece of 
hose at the other. This combination is known 
as a hydrometer syringe. 

To use the hydrometer the bulb is squeezed, 
the nozzle placed in the liquid and then the 
bulb released. As the bulb is released, the 




219 


STORAGE BATTERIES 


liquid is drawn into the glass tube and floats 
the hydrometer. The specific gravity can then 
be read at the surface of the electrolyte when 
the hydrometer floats free of the sides of the 
syringe, and the syringe is held in a vertical po¬ 
sition. After the reading is taken, the bulb is 
compressed to expel the liquid from the 
syringe. 



FIG. 223 


Temperature Correction for Hydrometer 

The scale on the battery hydrometer is grad¬ 
uated and set to register correctly only when 
the temperature of the electrolyte is 70 
degrees Fahrenheit. As the temperature of 
the electrolyte increases.it becomes less dense, 
so that the hydrometer will sink deeper into it. 
Therefore, if the temperature of the electrolyte 
is above 70 degrees the hydrometer will reg¬ 
ister low. A temperature correction may be 
made by adding one point to the hydrometer 
reading for each three degrees above 70 de¬ 
grees F. As the temperature of the electrolyte 
becomes lower, its density increases until a 
temperature is reached that is slightly above 
the freezing temperature of the electrolyte. 
Therefore, if the temperature of the electrolyte 


is below 70 degrees, the hydrometer will reg¬ 
ister high. The temperature correction may be 
made by substracting one point from the 
hydrometer reading for each three degrees be¬ 
low 70 degrees Fahrenheit. The variation in 
temperature of the electrolyte makes only a 
slight variation in the hydrometer reading, and 
so where only the approximate specific 
gravity is wanted, the temperature correction 
can be neglected. 

Ampere Hour Capacity of the Storage Battery 

The capacity of the storage battery is given 
in ampere-hours, which is the number of hours 
times the rate in amperes that the battery is 
discharged. 

The S. A. E. standards require that batteries 
for combined lighting and starting service shall 
have two ratings. The first indicates the 
lighting ability and shall be the capacity in 
ampere hours of the battery when discharged 
continuously at a 5-amp. rate to a final voltage 
of 1.8 per cell, the temperature of the battery 
at the beginning of the discharge being 80 
deg. Fahr. 

The second rating shall indicate starting 
ability and shall be the rate in amperes at 
which the battery will discharge continuously 
for 20 minutes to a final voltage of not less 
than 1.65 per cell, the temperature of the bat¬ 
tery at the beginning of the discharge being 80 
degrees Fahr. 

For example, a battery discharging for 16 
hours at a 5 ampere rate has an 80 hour am¬ 
pere-hour capacity. The ampere-hour ca¬ 
pacity decreases slightly as the temperature of 
the battery is lowered. 

Action of Storage Cell on Discharge 

When a storage cell is fully charged, the ac¬ 
tive material in the positive plate is lead per¬ 
oxide (PbO,) and the active material in the 
negative plate is pure spongy lead (Pb). The 
electrolyte is a solution of sulphuric acid, 
(H.SO,^). (See Fig. 224.) When the plates 
are immersed in the electrolyte, a chemical 
action takes place between the active materials 
of the plates and the acid of the electrolyte. 
This chemical action forces the electricity from 
the plate having the pure spongy lead for 
the active material, to the plate having lead 
peroxide for the active material and so charges 
the lead peroxide plate to a higher pressure 
than the lead plate. An explanation of the 
chemical action is given in the following. 

Each molecule of the acid is composed of 
two atoms of hydrogen, one atom of sulphur, 
and four atoms of oxygen (H^SOJ. When the 
acid is mixed with water, according to a theory 
in chemistry, the acid dissociates; that is, each 
molecule breaks into two ions—a hydrogen ion. 













220 


ELEMENTS OF ELECTRICITY 


composed of the two atoms of hydrogen (H 2 ), 
and a sulphion composed of an atom of sul¬ 
phur and four atoms of oxygen (SO 4 ). The 
hydrogen ions carry positive charges and the 
sulphions carry negative charges. So long as 
the plates are not immersed in the solution, 
the solution remains neutral since there are 
the same number of ions with positive charges 
as ions with negative charges. 

Each molecule of lead peroxide, the active 
material of the positive plates, is composed of 
one atom of lead and two atoms of oxygen 
(PbOa). The pure spongy lead (Pb), the active 
material of the negative plates, is an element 
itself and not a chemical combhiation of ele¬ 
ments. 

When the plates are immersed in the elec¬ 


positive charges with them as they combine 
with the sulphions. These positive charges are 
neutralized by the negative charges which the 
sulphions carry. As the atoms of lead from 
the negative plate combine with the sulphions, 
the negative plate is charged with a negative 
pressure. As each atom of lead of the positive 
plate combines with a sulphion, two atoms 
of oxygen combine with four atoms of hydro¬ 
gen. Therefore as a positive charge is sub¬ 
tracted from the positive plate by an atom of 
lead combining with a sulphion, two negative 
charges are subtracted by the two atoms of 
oxygen which combine with the hydrogen; and 
since four atoms of hydrogen combine with 
the two atoms of oxygen, two of the positive 
charges which the hydrogen atoms carry are 




discharging. CHARGING. 

FIG. 224 


trolyte, the affinity of the sulphions for the 
lead causes them’ to combine with atoms of 
lead from both plates. For each sulphion that 
combines with an atom of lead from the plates, 
a molecule of lead sulphate (PbSO^) is formed 
and two atoms of hydrogen are liberated from 
the acid. For each atom of lead in the positive 
plate that combines with a sulphion, two atoms 
of oxygen are liberated from the lead peroxide. 
Since the sulphions combine with atoms of 
lead from both plates the hydrogen is lib¬ 
erated twice as fast as the oxygen. The 
hydrogen and oxygen combine—two atoms of 
hydrogen to one of the oxygen (H 2 O)—form¬ 
ing water. 

The atoms of lead from the plates carry 


not neutralized, hence are added to the positive 
plate. 

When the charge on the positive plate 
reaches a pressure about 2.2 volts higher than 
that on the negative plate, the chemical action 
practically stops. The negative charge left on 
the negative plate so attracts the positive 
charges which the atoms of oxygen carry, that 
the atoms of lead are prevented from combin¬ 
ing 'With the sulphions. The positive charge on 
the positive plate so attracts the negative 
charges which the atoms of oxygen carry, that 
the oxygen is bound to the plate and the hydro¬ 
gen ions are repelled. The oxygen then cannot 
combine with the hydrogen and the lead that 
is held in combination with the oxygen cannot 


























































































STORAGE BATTERIES 


221 


combine with the sulphions, hence the chemical 
action at the positive plate is stopped. If a 
wire connects the positive plate to the negative 
plate, an electric current will flow through the 
wire from the positive plate to the negative. 
As the current flows, the charges become 
weaker (the difference in electrical pressure on 
the two plates becomes less) and the chemical 
action takes place at a rate that is proportional 
to the strength of the current. 

The chemical action between the acid and 
the active materials of the plates reduces the 
electrolyte to a weak solution of acid and the 
active materials to lead sulphate. When the 
discharge has been continued till the differ¬ 
ence in the electrical pressures on the plates 
has dropped to about 1.8 volts, the discharge 


negative terminal of the cell connected to the 
negative terminal of the generator. 

Action of Storage Cell on Charge 

When a storage cell is in a discharged state, 
the active material on both plates is lead sul¬ 
phate (PbSOj), and the electrolyte is mostly 
water, being only a very weak solution of sul¬ 
phuric acid. If now the cell is connected to a 
generator, positive plate to the positive ter¬ 
minal of the generator and the negative 
plate to the negative terminal of the gen¬ 
erator, the generator can be made to force 
current back through the cell, in at the 
positive plate through the electrolyte from the 
positive plate to the negative plate, and out of 
the negative plate. As the current is forced 



rate being about one-tenth the ampere-hour 
capacity of the cell, the cell is considered 
to have reached the safe limit of discharge. 
To recharge- the cell it is necessary to 
force an electric current back through the 
cell in the reverse direction. This is done 
by connecting the cell to a generator with 
the positive terminal of the cell connected to 
the positive terminal of the generator and the 


through a cell in this direction, the chemical 
action which takes place on discharge is re¬ 
versed; the sulphions are driven out of the 
plates; the water in the electrolyte is broken 
up into hydrogen and oxygen; the hydrogen 
ions are caused to unite with the sulphions 
coming from the plates and form molecules of 
acid, and the oxygen is caused to travel to the 
positive plate and unite with the lead forming 























































222 


ELEMENTS OF ELECTRICITY 


lead peroxide. Continuing this action will in 
time, reduce the negative plate to a pure 
spongy lead, the positive plate to lead peroxide, 
and form enough acid in the solution to in¬ 
crease the strength of electrolyte to what it 
should be when cell is fully charged. When 
this condition is reached the cell is in a charged 
state, and is again capable of forcing current 
through a circuit for a given time. 

During the latter part of the charge of a stor¬ 
age cell, water is broken up into hydrogen and 
oxygen faster than the sulphions are driven out 
of the plates, resulting in more hydrogen being 
liberated than there are sulphions to unite with 
it and more oxygen being liberated than there 
is lead in the positive plate to combine with 


turer, and sometimes marked on the name 
plate. If the charge rate is not stamped on 
the name plate, the starting rate may be taken 
as one tenth the ampere-hour capacity of the 
battery. These rates are for the first half 
of the charge, and should be reduced to one- 
half this rate during the last half of the charge. 

To Determine Polarity 

The polarity of a battery, or of the charging 
wires can be determined by any one of several 
methods. Two methods of accomplishing this 
are given in the following. 

Insert the two ends of the conductors in a 
glass of water which contains a small amount 
of acid or common salt. (See Fig. 226.) The 



FIG. 226 


it. The excessive hydrogen and oxygen es¬ 
cape from the cell in the form of gas. As the 
hydrogen and oxygen escape from the cell, the 
electrolyte is caused to bubble, or “gas.” Re¬ 
ducing the rate electricity is forced through 
the cell during the last half of the charge, 
prevents excessive gassing. Gassing of the 
electrolyte, so long as the current is not being 
forced through the cell at too high rate, is an 
indication that the cell is nearly charged. 

Storage cells should not be charged at too 
high rate. If the charge rate is too high, the 
cells will become heated and damaged and the 
electrolyte will be caused to gas excessively, or 
“boil.” The charge rates for storage bat¬ 
teries are usually specified by the manufac- 


passage of current through the water separates 
it into its constituent parts, hydrogen and 
oxygen. The hydrogen follows the cur¬ 
rent to the negative wire forming bubbles 
about it. The oxygen goes against the current 
forming bubbles about the positive wire. Since 
the volume of hydrogen is twice the volume of 
oxygen, the greater number of bubbles will 
rise from the negative wire. 

The right hand illustration shows the volt¬ 
meter method. The voltmeter must have 
proper capacity to measure the voltage of the 
lines across which it is to be connected. The 
positive terminal of the voltmeter is marked. 
Touch the wires lightly to the terminals to see 
if the needle moves across the scale in the 

































STORAGE BATTERIES 


223 


correct direction. If it does, the positive termi¬ 
nal of the voltmeter is then connected to the 
positive line. 

Battery Charging 

To charge a battery, connect its positive 
terminal to the positive -terminal of the 
charger, and its negative terminal to the nega¬ 
tive terminal of the charger. (A scheme for 
connecting a bank of lamps to be used as a 
charging resistance where 110 volts direct cur¬ 
rent is available is shown in Fig. 225). Adjust 
the charging resistance, or if a motor-genera¬ 
tor is used, adjust the voltage, so that the 
current is sent through the battery at the 
proper charging rate. 

Continue the charge at this rate until 
the specific gravity of the electrolyte comes 


heit, the charging rate must be reduced or the 
battery taken off of charge and allowed to cool. 
If the electrolyte gases excessively during the 
first part of the charge, the charging rate is too 
high and must be reduced. 

When storage batteries are allowed to 
stand for sometime in a discharged condition, 
or the electrolyte is permitted to get below 
the top of the plates, the sulphate on the 
plates so hardens that the charging current 
will not drive the sulphions out of the plates 
at the normal rate. If then, the battery is 
placed on charge at the full charging rate, the 
electrolyte will gas excessively and the battery 
will heat. Batteries in this condition (sul- 
phated) must be put on a long slow charge. 

If, at the end of the charge of a battery, the 
specific gravity of the electrolyte is above 1.300, 


CHARGED. 



FIG. 227 


up to between 1.225 and 1.250, then re¬ 
duce the charging rate one-half. Continue 
the charge at this rate until there is no 
noticeable rise in the specific gravity of the 
electrolyte for a period of four or five hours, 
and the back E. M. F. is 2.5 volts per cell. The 
specific gravity of the electrolyte should then 
be from 1.275 to 1.300. (See Fig. 227.) If at 
any time during the charge, the temperature 
of the battery goes above 105 degrees Fahren- 


there is too much acid in the electrolyte and 
some of the electrolyte should be drawn 
from the cells and replaced with distilled 
water. This condition is very likely the result 
of an attempt to charge the battery by add¬ 
ing acid. NEVER ATTEMPT TO CHARGE 
A STORAGE BATTERY BY ADDING ACID 
TO THE ELECTROLYTE. A battery will 
operate when its specific gravity is above 1.300, 
but then the electrolyte is so strong with acid 



































































































































224 


ELEMENTS OF ELECTRICITY 


that the grids will become corroded and the 
separators burned. If the grids corrode, the 
active material is likely to be cracked off, re¬ 
ducing the capacity of the battery. If the 
separators become burned, or charred by the 
acid, they will crumble and the plates will 
break through them, short-circuiting the cells 
internally. 

If at the end of the charge the specific gravity 
is below 1.275 the electrolyte is weak. 
This may be due to cracked jars which 
permit the electrolyte to leak out, or to 
filling the cells too full when adding dis¬ 
tilled water, and so causing them to overflow 
when charging begins. If the bottom of the 
battery box is rotted, one or more of the jars 
are likely to be cracked. If the terminals of the 
battery are corroded, and the top of the box is 
rotted, the cells are likely overflowing, or the 
cover-plates are not properly sealed in the jars. 
If there are cracked jars in a battery, or the 
cover-plates are not properly sealed in the jars, 
the services of a battery-repairman are requir¬ 
ed. After new jars have been placed in a bat¬ 
tery, or the cover-plates properly sealed in the 
jars, the battery-repairman should make the 
necessary adjustment of the electrolyte. 

The specific gravity not coming up to 1.275, 
when the battery is charged, may be the re¬ 
sult of sulphated plates. When the plates be¬ 
come sulphated, it is seldom possible to drive 
all of the sulphate out of the plates by one 
charge, and as a result there will not be enough 
acid formed during a charge to bring the spe¬ 
cific gravity of the electrolyte up to 1.275. But 
after the battery has been discharged and 
charged a few times with proper care, all of 
the sulphate will, in time, be loosened so that it 
will be driven out of the plates during charge. 
In old batteries, the specific gravity of elec¬ 
trolyte is not so likely to come up as high on 
charge as that in new batteries, since the plates 
shed with use and the active material is lost. 

The charging of a battery should nol be 
continued very long after it reaches a fully 
charged condition. Charging a battery after it 
has reached a fully charged condition, loosens 
the active materials causing them to fall to 
the bottom of the jars, and oftentimes heats 
the battery, damaging it and shortening its 
life. Overcharging storage batteries causes 
considerable damage. 

Adding Water 

Distilled water should be added to the cells 
about twice a month to keep the electrolyte 
above the tops of the plates. It is not neces¬ 
sary to add acid, as the acid does not leave the 
cell on either charge or discharge, and does not 
evaporate. Water evaporates from the cells 


and is also lost when the gassing takes place 
while the battery is charging. 

If the specific gravity of the electrolyte is to 
be measured, do so before the water is added; 
or, if water has just been added to the cells, 
charge the battery a while to mix the water 
with the electrolyte, before measuring the 
specific gravity. If the weather is cold, 
temperature below freezing, the battery 
should always be charged for a while after 
the water is added. The water is lighter than 
the electrolyte and will remain on top unless 
mixed with the electrolyte. The gassing of the 
electrolyte mixes it with the water. If the 
water remains on top it is likely to freeze and 
burst the jars. 

Corroded Terminals 

If the battery terminals corrode, the sub¬ 
stance formed by the corrosion should be 
loosened and removed. This can be done by 
moistening it with a solution of bicarbonate 
of soda, washing soda and water, or a rag 
wet with ammonia. Then brush the termi¬ 
nals with a wire brush. Corroded terminals may 
be cleaned by scraping with a knife, but when 
scraped, care must be taken not to scrape off 
the lead. (Scraping is not recommended.) After 
the terminals are cleaned, they should be cov¬ 
ered with vaseline. The top of the battery 
should be cleaned with a rag moistened with 
ammonia and then covered with vaseline. Do 
not let the cleaning solution get into the cells 
as it will neutralize the acid within the cells 
in the same manner that it does the acid on 
the top and terminals. 

Freezing Temperatures 

The freezing temperatures for the electrolyte 


are as follows: 
Specific 

Freezing 

Gravity. 

• Temperatures. 

1.000 (Water) . 

Above Zero. 
.Plus 32 

Degrees 

1.050 . 

. ” 26 

>> 

1.100 . 

. ” 18 

>> 

1.150 . 

. ” 15 

99 

1.200 . 

Below Zero. 

99 

1.250 . 

. ” 60 

99 

1.275 . 

. ” 90 

99 

1.300 . 

. ” 97 

99 


A battery when not in use should not stand 
at freezing temperatures, even though it 'is 
charged, as the acid settles to the bottom, 
leaving a weak solution at the top that will 
freeze at higher temperatures than given 
above. 

Batteries used in tropical climates must 
operate at higher temperatures than those used 











ELECTROMAGNETISM 


225 


in the temperate climates and for this reason 
the electrolyte is not as strong. 

Storing Batteries 

Storage batteries, when not in use, should 
be stored in a cool dry place. The temperature 
should be about 70 degrees Fahrenheit. A 
freshening charge should be given the battery 


every month or six weeks. A storage battery 
can be left for as long as six months without 
damage to battery, but at the end of this time 
it is necessary to give the battery a long slow 
charge before putting it into service. The 
battery will not be as active as before it was 
allowed to stand until it is charged and dis¬ 
charged several times. 


ELECTROMAGNETISM 


An electric current always produces a mag¬ 
netic field; that is to say, electricity in motion 
sets up magnetic lines of force in the space 
immediately surrounding the conductor in 
which it is fiowlng. The lines of force fiow in 
circular paths around the conductor. The di¬ 
rection of the fiow of the magnetic lines of 
force bears the same relation to the direction 
of the fiow of current, as the direction of rota¬ 
tion of a corkscrew bears to its backward and 
forward movement. Looking at the end of 
the wire, if the conductor is carrying current 
away from the observer, the magnetic lines of 
force fiow around it in the same direction 
as the corkscrew must be turned to turn it 
ihto a cork. If the conductor is carrying cur¬ 
rent toward the observer, the lines of force fiow 
around it in the same direction as the cork¬ 
screw must be turned to turn it out of the 
cork. 

When the direction of the fiow of the cur¬ 
rent in a conductor is known the direction of 
the fiow of the lines of force around the con¬ 
ductor may be determined by the following 
right hand rule. Grasp the conductor with the 
right hand so the thumb points in the direc¬ 
tion of the fiow of current, and the fingers will 
then bend in the direction of the fiow of the 
lines of force. 


Magnetic Field About a Straight Conductor 

Fig. 228 gives a conception of the mag¬ 
netic field set up about a straight conductor 
carrying current from right to left. This figure 
is merely illustrative and the idea that the 
magnetic field only extends out for a short 
distance from the conductor must not be 
formed. The magnetic field extends to an 
indefinite distance from the conductor, though 
the strength of the field becomes weaker and 
weaker as the distance from the conductor in¬ 
creases. The change in density of the field 
is inversely proportional to the distance from 
the conductor. In practice, the field becomes 
so weak only a short distance from the 
conductor that it is usually assumed there 
is no field except near the conductor. If a 
compass needle is placed beneath the conduc¬ 
tor in Fig. 228, it will point toward the ob¬ 
server. If the compass is placed above the 
conductor, it will point away from the ob¬ 
server. This shows that the magnetic lines 
of force flow toward the observer beneath the 
conductor and away from the observer above 
the conductor. The flow of the magnetic lines 
• of force around the conductor is always at 
right angles to the flow of the electric current. 
They do not flow along the conductor but flow 
around it. 



FIG. 228 














226 


ELEMENTS OF ELECTRICITY 


Strength of Field Depends Upon Strength 
of Current 

The strength of the magnetic field set up 
about the conductor is directly proportional to 
the strength of the current. Any variation in 
the strength of the current causes a corre¬ 
sponding variation in the strength of the mag¬ 
netic field about it. If the strength of the cur¬ 
rent is increased the strength of the field will 
be increased; or if the strength of the current 
is decreased the strength of the field will be 
decreased. If the current is interrupted the 
field collapses, the instant the flow of electricity 
stops. The strength of the field does not de- 
depend upon the size of the conductor or the 
material of which it is made. 


Parallel Conductors Carrying Current in Same 
Direction 

Fig. 229, illustration (C) shows a section of 
three parallel conductors carrying current in 
the same direction and the manner in which 
the magnetic lines of force flow around all of 
the conductors instead of around each one 
separately. The magnetic lines of force flow¬ 
ing around all three conductors tend to pull the 
conductors together. Parallel conductors car¬ 
rying current in the same direction attract one 
another. 

Parallel Conductors Carrying Current in 
Opposite Directions 

Fig. 229, illustration (D) shows a section 



(0 0 ®) 


c. 



N 


/T\/T\/TN^T\/T\rt\^T\/>T\/^ 


/ ( ©©©O©O©©0 )\ 


FIG. 229 


E 


Direction of Field Depends Upon Direction of 
Current 

Fig. 229, illustration (A) shows a cross-sec¬ 
tion of a conductor carrying current away 
from observer and the magnetic lines of force 
flowing around the conductor in a clockwise 
direction. Illustration (B) shows the cross-sec¬ 
tion of a conductor carrying current towards 
observer and the magnetic lines of force flow¬ 
ing around the conductor in a counter clock¬ 
wise direction. These figures are illustrative 
and show that a change in the direction of 
the flow of current causes a change in the 
direction of the magnetic lines of force which 
flow around the conductor. 


through two parallel conductors carrying cur¬ 
rent in opposite directions and the manner in 
which the magnetic lines of force crowd in be¬ 
tween the conductors. The cross in the center 
of one conductor indicates that the current is 
flowing away from observer. The magnetic 
lines of force.flow around this conductor in a 
clockwise direction. The dot in the center of 
the other conductor indicates the current is 
flowing toward observer. The magnetic 
lines of force flow around this conductor 
in a counter clockwise direction. The mag¬ 
netic lines of force crowd in between the 
conductors and as one line repels another, 
a force is set up that tends to push the con- 




























ELECTRO IM AG NETISM 


227 


ductors apart. Parallel conductors carrying 
current in opposite directions repel one 
another. 

Magnetic Field Set Up by Current in a Coil 

When an electric current is passed through 
a coil of wire, magnetic lines of force are set 
up which flow through the coil, out at one end, 
around the coil and back into the coil at the 
other end. A coil of wire carrying current is 
much the same as a bar magnet. It has a 
north pole and a south pole. If the coil is 
suspended free to turn while it is carrying 
current, it will come to rest with one end to- 


a solenoid. The strength of the magnetic 
field set up by a helix depends upon the num¬ 
ber of turns, the number of amperes and shape 
of helix. The number of amperes multiplied 
by the number of turns equals the number of 
ampere-turns in a helix. 

Ampere-Turns 

One ampere passing through one turn is one 
ampere-turn. One ampere passing through 
two turns will be two ampere-turns; two am¬ 
peres passing through one turn will be two am¬ 
pere-turns. One ampere passing through two 
turns sets up as strong magnetic field as two 



wards the north and the other end towards 
the south. If the coil is brought near mag¬ 
netic material while it is carrying current, it 
draws, or tends to draw, the magnetic material 
into it. Fig. 229, illustration (E) shows a sec¬ 
tion through a coil and the direction in which 
the magnetic lines of force are set up. The 
polarity of a coil carrying current may be 
determined by the following right hand rule. 
Grasp the coil with the right hand so the 
fingers bend in the direction the current flows 
around coil, and the thumb will then point to 
the north pole. 

Helix Solenoid 

A coil that will carry an electric current is 
called a helix. If the length of the coil is 
greater than its diameter it is usually called 


amperes passing through one turn. Since the 
magnetic field is proportional to the ampere- 
turns, they may be taken as a measure of the 
magnetic strength of a helix. 

Advantage of Many Turns 

Consider two coils which will be referred to 
as coil “A” and coil “B.” Both are wound of 
the same sized wire, and are the same 
diameter. Coil “A” has 500 turns and coil 
“B” has 1,000 turns. Twice as much wire 
must be used for coil “B” as for coil “A” 
and so its resistance is twice as great. If coil 
“A” has one ohm resistance, coil “B” then has 
two ohms. Coil “A” when connected to the 
terminals of a six-volt battery will carry six 
amperes, [6, (number of volts) 1, (number 
of ohms) = 6, (number of amperes)] and so 










































































228 


ELEMENTS OF ELECTRICITY 


has three thousand ampere-turns [6, (number 
of amperes) x 500, (number of turns) = 3000, 
(number of ampere-turns)]. The power used 
by “A” is equal to 6, (the number of volts), 
multiplied by 6, (the number of amperes), 
equals 36, (the number of watts). Coil “B” 
when connected to the same battery carries 
three amperes [6, (number of volts) -f- 2, 
(number of ohms) = 3, (number of amperes)] 
and has three thousand ampere-turns [3, 
(number of amperes) x lOOO, (number of 
turns) = 3000, (number of ampere-turns)]. 
The power used by “B” is equal to 6, (the 
number of volts) multiplied by 3, (the num¬ 
ber of amperes) equals 18, (the number of 
watts). Coil “B” has the same number of 
ampere-turns as coil “A,” consequently it sets 
up practically as strong a field, but the power 



required for coil “B” is only half the power re¬ 
quired for coil “A.” The advantage then of 
more turns in a coil is that practically the 
same strength of magnetic field can be pro¬ 
duced with less power consumption. 

From the comparison of these two coils 
it can be seen that, were it not for the coil heat¬ 
ing, the short circuiting of turns would not 
change its ampere turns, since the resistance 
decreases in proportion to the number of turns 
short circuited, causing the current to in¬ 
crease, thereby keeping the ampere-turns ap¬ 
proximately constant. 

The strength of the magnetic field set up 
by a helix depends to a great extent upon its 


length. The longer the helix the farther the 
lines of force must flow to complete their cir¬ 
cuit and so the higher the reluctance of the 
circuit. If the helix is wound compactly, a 
stronger field will be set up for a given number 
of ampere turns than will be set up if the helix 
is longer than its diameter. 

Electromagnet 

When an insulated conductor is wound 
around a soft iron core an electromagnet is 
formed. When current is sent through the coil, 
the magnetic lines of force which it sets up 
flow through the core and magnetize it. By 
using the core, from several hundred to sev¬ 
eral thousand times as many magnetic lines 
of force are set up as would be possible without 
the core. Fig. 230, upper left, shows a straight 



core type electromagnet. In this type, the mag¬ 
netic lines of force must flow in one direction 
through the air from one pole to the other to 
complete their circuit, hence the reluctance is 
high. This type core is used for induction 
coils. The illustration at right shows a “U” or 
horseshoe core. The ends of this core are not 
so far apart, hence the reluctance is not so 
high. This type core is used for magnet 
chargers and lifting magnets. The illustra¬ 
tion at bottom shows a closed core. This type 
core is not used for lifting magnets, as the 
magnetic circuit is closed and there are prac¬ 
tically no poles. This type core is used to 
some extent in induction coils. It gives a 





































ELECTROMAGNETIC INDUCTION 


229 


magnetic circuit of low reluctance, hence, 
more magnetic lines of force are set up for a 
given number'of ampere-turns. 

Polarity of Electromagnet 

The polarity of an electromagnet depends 
upon the direction the current flows around 
the core. (See illustrations in Fig. 231.) The 
right hand rule by which the polarity of a coil 
is determined can be used to determine the 
polarity of an electromagnet. Some electro¬ 
magnets have two windings on the core as 
shown at the lower left in Fig. 231. As long 
as the current is passed around the core in 
the’same direction in both windings, both wind¬ 
ings assist in magnetizing the core. If the cur¬ 
rent is passed around the core in one winding 


in the opposite direction to the flow of the cur¬ 
rent in the other winding, one then tends to 
neutralize the other. If there are the same 
number of ampere-turns in both windings, the ^ 
core will not be magnetized. If there are more 
ampere-turns in one winding than in the other, 
the polarity of the core depends upon the direc¬ 
tion the current flows in the winding having the 
greater number of ampere-turns. The current 
in the other winding then merely tends to 
weaken the magnetic strength of the core. 

Strength of Electromagnet 

The strength of the electromagnet depends 
upon the number of ampere-turns in the coils, 
and the size and shape of the core and the 
material of which it is made. 


ELECTROMAGNETIC INDUCTION 


When a conductor cuts magnetic lines of 
force, an E. M. F. is induced in it that is propor¬ 
tional to the rate at which the lines of force 
are cut. The conductor can be moved and the 
field held stationary; the field moved and the^ 
conductor held stationary; or both conductor 
and field moved—but in any case the move¬ 
ment of one with relation to the other must be 
such that the conductor cuts the lines of force. 
If the relative movement of the conductor is 
parallel to the lines of force, no E. M. F. is in¬ 
duced in the conductor. 

Strength of Induced E. M. F. 

When a conductor cuts one hundred million 
lines of force per second during its movement 
with respect to the magnetic field, an E. M. F. 
of one volt is induced in the conductor. If the 
conductor cuts lines of force at the rate of two 
hundred million per second, the induced E. M. 
F. is two volts; and if the conductor cuts six 
hundred million lines of force per second, the 
induced E. M. F. is six volts. If the conductor 
that cuts the magnetic lines of force is part of 
a circuit, a current is produced equal in 
strength to the induced E. M. F. divided by 
the total resistance of the circuit. 

Direction of Induced E. M. F. 

The direction of the induced E. M. F. de¬ 
pends upon the direction of magnetic lines of 
force flow, and the direction the conductor 
moves across the field. One of the best rules 
for remembering the relation between the di¬ 
rection of the flow of the magnetic lines of 
force, the direction that the conductor moves 


across the magnetic field, and the direction of 
the induced E. M. F., is known as Fleming’s 
Right Hand Rule. The rule is as follows: 
Place the thumb, first finger and middle finger 
of the right hand all at right angles to each 
other; turn the hand into such a position that 
the thumb points in the direction of the move¬ 
ment of the conductors and the first finger in 
the direction the magnetic lines of force flow, 
then the middle finger will point in the direc¬ 
tion of the induced E. M. F. 

Illustrations in Fig. 232 show the relation 
between the flow of the lines of force, the 
direction a conductor moves across the field 
and the direction of the induced E. M. F. In the 
upper left illustration the north pole of the 
horseshoe magnet is at the bottom, and the 
south pole at the top. The general direction of 
the flow of the lines of force then is upward. A 
cross-section of a conductor which is being 
moved between the poles is shown. The direc¬ 
tion of the movement of the conductor is from 
right to left. The cross in the center of the 
conductor indicates that the induced E. M. F. 
would be forcing the current away from ob¬ 
server. The dotted circle around the conduc¬ 
tor represents the magnetic lines of force that 
would be set up by the induced current in the 
conductor. Because of lines of force set up by 
the induced current, the lines of force between 
the poles of the magnet are crowded ahead of 
the conductor and compressed on the side 
moving against them. These lines of force 
being compressed on this side of the conduc¬ 
tor and flowing upward, may be thought of as 
tending to set up a magnetic whirl around the 




230 


ELEMENTS OF ELECTRICITY 


conductor in a clockwise direction which, if 
set up, will cause current to flow through the 
conductor away from the observer. 

Illustration at lower right shows another re¬ 
lation between the direction of the flow of the 
magnetic lines of force, the direction of the 
movement of the conductor and the direction 
of the induced E. M. F. when the conduc¬ 
tor is moving out from between the poles. Mov¬ 
ing in this direction, the induced E. M. F. causes 
the current to flow through the conductor to¬ 
wards the observer. The magnetic lines of 
force set up by the magnet are compressed on 
the opposite side of the conductor to that 
shown in upper left, hence they tend to set up a 
magnetic whirl about the conductor in a 
counter-clockwise direction, which, if set up, 
will cause current to flow toward the observer. 


If the current is increasing in strength, more 
magnetic lines of force are expanding from 
the centre of the conductor much like “ring 
waves” expand from a point where a stone 
is dropped in a body of water. As these mag¬ 
netic lines of force expand from the centre of 
the conductor, they are cut by the conductor, 
inducing an E. M. F. in it. The direction of 
the flow of the magnetic lines of force set up by 
the current, and the direction the conductor 
cuts them as they expand is always such that 
the induced E. M. F. opposes the increase in 
the strength of the current. 

If the strength of the current is decreased, 
the magnetic field also decreases; that is, lines 
of force collapse toward the centre of the con¬ 
ductor. As the lines collapse,'they are cut by 
the conductor, and so induce an E. M. F. in it. 



Self-Induction 

Whenever the strength of the current flow¬ 
ing through a circuit is caused to change, an 
E. M. F. which opposes the change is induced. 
If the strength of the current is increased, 
while the increase is taking place, an E. M. F. 
is induced which is against the flow of current. 
If the strength of the current is decreased, 
while the current is decreasing, an E. M. F. is 
induced which tends to keep the current flow¬ 
ing in the same direction and at the same 
strength. These E. M. F’s. are induced in the 
circuit by the movement with relation to con¬ 
ductor of the magnetic lines of force set up by 
the current. 


The direction of the lines of force set up by 
the current and the direction they are cut by 
the conductor when they collapse, is always 
such as to induce an E. M. F. that tends to keep 
the current flowing in the same direction and 
at the same strength. 

The inducing of an E. M. F. in a circuit by 
changing the strength of the current flowing 
through it, is called self-induction. 

Self-induction of an electric circuit is 
analagous to the property of matter called 
inertia. When an electric circuit is closed, the 
strength of the current does not reach its full 
strength (volts divided by ohms) the instant 
the circuit is closed, but gradually “builds up” 





































ELECTROMAGNE TIC INDUCTION 


231 


to full strength. When a circuit is opened the 
flow of electricity does not stop the instant the 
break occurs, but instead, a spark, or arc is 
usually produced at the point where the circuit 
is broken and the flow of electricity is quickly 
but not instantly stopped. Stopping a flow of 
electricity through a circuit by opening a 
switch is much like holding a number of planks 
in the path of a moving car to bring it to a 
standstill. The self-induced E. M. F. drives the 
electricity through the thin air-gap, between 
the switch blade and jaw, when the switch is 
first opening, just as the momentum of the car 
will cause it to crash through a number of the 
planks before being brought to a standstill. 

The self-induction of long straight conduc¬ 
tors is very low since the lines of force which 
are set up by the current, cut the conduc- 


self-induction) causes the current to lag so 
much that it will not reach full strength in a 
short space of time, only coils of compara¬ 
tively few turns are used in circuits which are 
rapidly opened and closed. 

Mutual Induction 

Fig. 233 shows two circuits, one of which is 
called the primary circuit and the other the 
secondary circuit. The primary circuit in¬ 
cludes a dry cell, a switch and a long con¬ 
ductor forming a loop. The secondary circuit 
is made up of a long conductor and a milli- 
voltmeter. One side of the primary circuit 
lies parallel with one side of the secondary 
circuit. 

When the switch in the primary circuit is 
closed, the E. M. F. of the cell causes current 



Q 


SEICONDARY 



> --- V ■' ' 


■ ! ^ 


^ > 

V V r.-.\ / .-A 



< ^ V ^~y -—4' 

>■ ; V >■ /» / -■ A 


^ ( r. \ 

J / 

■'y. '''y 

' \ ' / 'C / 

/y /y 

i 

/ 

Ky yy Ky Vy V/ 

PRIMARY 

fn=n3=:^'.^ /y. / 


' V/ K'/ 

'^1/' M'' 

* 

ua r. ; : r. ^ 1 y. ; / 4% 

k;/ 

V'V 


' Ky 

s 

y; yj 

FIG. ^ 

1 1 L' j \ 'y 1 

/ N / 

533 

' — i 


r ■■rv 1 ; v > L 0 i » 'J 

V/ 


tor once when they expand, and once when 
they collapse. The self induction of coils is 
comparatively high, varying as the square of 
the number of turns. The self-induction 
of a coil may be made very high by winding it 
on a soft iron core. If the coil is wound on a 
soft iron core more lines of force are set up 
by the current, hence there are more to be cut 
by the turns of the coil as they expand; and, 
when the current is interrupted there are more 
lines to be cut by the turns of the coil as they 
collapse. Since a coil of many turns (high 


to flow through the circuit, and as the current 
builds-up, magnetic lines of force expand from 
the centre of the conductor and flow around it. 
As the lines of force expand from the part of 
the primary wire that lies parallel to the 
secondary, they are cut by the secondary and 
induce an E. M. F. in it, causing current to flow 
through the meter, deflecting the needle. The 
direction of the induced current in the second¬ 
ary, as the lines expand, is opposite to that in 
the primary. 

When the switch in the primary circuit is 
































232 


ELEMENTS OF ELECTRICITY 


opened, the lines of force collapse to the cen¬ 
ter of the primary wire, and as they collapse 
they are again cut by the wire of the secondary 
circuit inducing E. M. F. in it. The current 
which flows through the secondary as a result 
of the induced E. M. F. during the collapse of 
the lines of force, is in the same direction as 
that in the primary. 

The inducing of E. M. F. in a secondary 
circuit by varying the strength of the current 
in a primary circuit is called mutual induction. 
Mutual induction is caused by expanding or 
collapsing lines of force and so takes place 


one of low voltage. As required for ignition, 
the high voltage must be sufficient to cause a 
spark to jump an air gap and the low voltage 
varies from 6 to 30 volts. 

The primary winding of the induction coil is 
connected in series with the battery or genera¬ 
tor, and some device such as a breaker or vi¬ 
brator which opens and closes the circuit. For 
the present consideration a switch may be used 
for closing and opening the circuit. The 
secondary is connected in series with a small 
air gap which in practice, is usually the gap of a 
spark plug. (See Fig. 234.) The figure is illus- 



while the current in one of the circuits is in¬ 
creasing or decreasing. 

A good example of an application of mutual 
induction is the high tension induction coil. 
The induction coil, sometimes called a trans¬ 
former, consists of: (1) Core—usually a bun¬ 
dle of soft iron wire; (2) Primary—a winding 
of a few hundred turns of about No. 18 or No. 
20 wire wound over the core, but insulated 
from it; (3) Secondary—a winding of several 
thousand turns of fine wire, about No. 36 or 
No. 38, which is wound over the primary but 
well insulated from it. The induction coil is 
used to produce a current of high voltage from 


trative and is not intended to show the num¬ 
ber of turns in either the primary or second¬ 
ary. The primary is shown in heavy lines and 
the secondary is shown in lighter lines. The 
relative position of core, primary, and second¬ 
ary and the method of connecting the ends of 
both primary and secondary to terminals are 
plainly shown. In actual construction the 
turns of the primary and secondary are wound 
as closely as the insulation will permit. 

Operation of Induction Coil 

When the switch is closed, the battery 
causes current to flow through the primary 


































































ELECTROMAGNETIC INDUCTION 


233 


circuit, which as it flows through the primary 
winding of the coil, magnetizes the core. As 
the core becomes magnetized, lines of force 
expand from the primary and are cut by the 
coils inducing an E. M. F’. in each turn of the 
secondary winding. The lines expand at a rate 
that, disregarding the losses due to resistance 
of wires, reluctance of core, etc., induces in the 
secondary an E. M. F. which is as many times 
the E. M. F. of the battery as the number of 
turns in the secondary are times the number of 
turns in the primary. If there are 100 times as 
many turns in the secondary as in the primary, 
the E. M. F. induced in the secondary is about 
100 times the E. M. F. of the battery. 

When the switch is opened, the current in 
the primary is interrupted, causing the lines of 
force to collapse. The flow of electricity is 
stopped in 1/20 to 1/100 the time required for 
the E. M. F. of the battery to build it up. Since 
the lines collapse 20 to 100 times as quickly as 
they expand, the E. M. F. induced in the sec¬ 
ondary when the primary circuit is broken is 
from 20 to 100 times as strong as the E. M. F. 
induced when the primary circuit is closed. If 
there are 100 times as many turns in the sec¬ 
ondary as in the primary, the E. M. F. induced 
in the secondary when the primary is broken 
may be from 2,000 to 10,000 times the E. M. F. 
of the battery. The secondary voltage of igni¬ 
tion coils is very high, from 12,000 to 30,000 
volts and even higher. This high E. M. F. in¬ 
duced in the secondary winding by the collapse 
of the magnetic lines of force is strong enough 
to drive electricity across the air gap that is in 
the secondary circuit. As the electricity is 
forced across the gap a spark is produced. 

The strength of the current in the secondary 
cannot be other than weak, since the watts 
in the secondary can never equal or be more 
than the watts in the primary. It is for this 
reason that the secondary terminals of an in¬ 
duction coil can be held in the hands without 
danger of severe shock or burn. 

The self-induced E. M. F. produced in the 
primary by the collapse of the lines of force 
tends to keep the primary current flowing, re¬ 
sulting in the current being forced across the 
gap between the switch contacts as they sep¬ 
arate. This prevents a quick collapse of the 
lines of force and causes a spark which burns 
the switch contacts. To reduce this sparking 
to minimum and at the same time effect- a 
quick interruption of the current, a condenser 
is connected parallel to the switch. 

Condenser 

If a metal plate is connected to the positive 
terminal of a battery and a similiar one is 
connected to the negative terminal of the bat¬ 


tery, the former will receive a positive charge 
and the latter will receive a negative charge. 
So long as the plates are some distance apart 
the charges are small. If the plates are brought 
near together, but not touching each other, 
there will be an attraction between the two 
unlike charges on the plates. The nearer the 
two plates are, the greater this attraction will 
be and the greater the charge on each plate 
will be, because the charge on one plate will 
draw a stronger charge on the other. The 
binding effect of one charge on the other 
makes it possible for the E. M. F. of the battery 
to draw a quantity of electricity from one plate 
and force it on the other. 

Two such metal plates insulated from each 
other form a simple condenser. The capacity 
of a condenser is determined by the quantity 
of electricity that can be stored on the posi¬ 
tive plate under a pressure of one volt. 
If enough electricity under a pressure of one 
volt can be stored on the positive plate to 
give an average current of one ampere for one 
second when discharged the condenser has a 
capacity of one farad. A condenser to have a 
capacity of one farad must be very large, so 
instead of using the farad as the common unit 
of capacity the microfarad is used. The micro¬ 
farad is one millionth of a farad. 

If air is used to insulate the plates, one from 
the other, it is difficult to keep the plates from 
touching, and it has been found that other 
materials will insulate the plates better and 
at the same time give the condenser a higher 
capacity. Paraffin paper and mica are both 
very good materials for placing between the 
plates and both can be made in comparatively 
thin sheets so the plates can be placed very 
close together and yet be well insulated from 
each other. If the condenser is made of tinfoil 
for the plates and paraffin paper for the insula¬ 
tion between the plates, the condenser can be 
rolled into a small roll so that it is very com¬ 
pact. If mica is used it is not necessary to 
make the plates so large since stronger charges 
will store on plates separated by mica than 
when separated by paraffin paper of the same 
thickness. 

It is hardly practical to construct two plates 
large enough to have the proper capacity for a 
condenser to be used in parallel to the switch. 
Instead, the condenser is made up of a number 
of plates. Alternate plates are joined together 
forming two groups of plates arranged similar 
to the positive and negative groups of the stor¬ 
age battery. Each group is connected to one 
of the terminals. 

The capacity of the condenser depends upon 
the size and number of plates and the thick¬ 
ness and kind of material used to insulate them 
from each other. The area of the plates can 



234 


ELEMENTS OF ELECTRICITY 


be increased either by using larger plates or 
more plates. The greater the area of the 
plates the higher the capacity of the con¬ 
denser. The closer the plates are together, 
that is, the thinner the insulating material be¬ 
tween them, the higher the capacity. Some 
insulating materials permit a stronger charge 
to be stored on the plates under a given pres¬ 
sure than others, so are better for this use. 

There is no circuit through a condenser be¬ 
cause the plates connected to one terminal 
are entirely separated by insulating material 
from the plates connected to the other termi¬ 
nal. If there is a circuit through a condenser, 
the condenser is either shorted or punctured 
and is worthless. A condenser can be charged 
by connecting it to a battery or a generator. If 
the charge stored in the condenser is to be of 
noticeable strength, the voltage of the battery 
or the generator should be something over a 
hundred volts. If the test points of a 110 volt 
D. C. test lamp are placed on the terminals of 
an ignition condenser it will be charged with 


right, pushing the rubber diaphragm to the 
position shown by the dotted line, thus permit¬ 
ting the water to continue flowing for an in¬ 
stant after the valve closes. As soon as the 
flow of the water is stopped, there is no longer 
any force to hold the diaphragm in this posi¬ 
tion and the action of the rubber, tending to 
flatten out, then crowds water back out of the 
chamber on the left, around through the cir¬ 
cuit, producing a momentary current in the 
reverse direction. 

In the condenser, as long as the switch is 
closed, the condenser is shorted and so is not 
charged. At the instant the switch opens, an 
air gap is formed in the primary circuit which 
resists the flow of electricity, causing it to 
crowd in on one set of plates of the condenser 
and charge them with a positive charge, and to 
be drawn from the other set of plates, leaving 
them with a negative charge. As the condenser 
is being thus charged, the current is permitted 
to continue flowing through the battery and the 
primary winding of the coil for an instant after 



strong enough charge to give a spark when dis¬ 
charged through a slight air gap. 

The action of a condenser around the switch 
is, in many ways, like that of a surge chamber 
around a valve in a hydraulic circuit similar to 
that shown in Fig. 235. The chamber above 
the valve is divided by a diaphragm made from 
a heavy sheet of rubber. With the pump run¬ 
ning and the valve open, the water which Alls 
the pipes, pump and surge chamber, is caused 
to circulate through the circuit formed by the 
pipes and the pump. If the valve is quickly 
closed, the force of the water in motion (mo¬ 
mentum) causes it to surge against the gate 
of the valve. By having the surge chamber 
connected around the valve, the force of the 
water on the valve is reduced considerably. 
Some of the water surges into the part of the 
surge chamber on the left and an equal volume 
passes out of the part of the chamber on the 


the switch contacts begin to separate. This 
delays the collapse of the lines of force until 
the switch has opened far enough so that the 
gap between the contacts will withstand the 
self-induced E. M. F. of the primary. As the 
condenser is charged, its back E. M. F. in¬ 
creases until it becomes equal to the E. M. F. 
of the battery plus the self-induced E. M. F. of 
the primary and so quickly stops the flow of 
electricity. As soon as the flow is stopped, the 
lines of force which it set up have collapsed 
and there is no self-induced E. M. F. to keep 
condenser charged, hence it discharges back 
through the primary. 

The momentary current back through the 
primary in the reverse direction, produced by 
this discharge, forces the lines of force set up 
by the residual magnetism of the core to col¬ 
lapse. 

The functions of the condenser are to reduce 
























IGNITION 


235 


sparking at the points where the primary cir¬ 
cuit is broken and to intensify the E. M. F. in 
the secondary by causing a quicker and more 
nearly complete collapse of the lines of force 
across the secondary. Without a condenser 


connected in parallel with the device used to 
open the primary circuit, the coil will seldom 
produce strong enough E. M. F. to break down 
the resistance of the air gap in the secondary 
circuit. 


IGNITION 


Electrical ignition systems for gas engines 
are divided into two classes; namely, low ten¬ 
sion ignition systems which are used on some 
tractor and stationary engines, and high ten¬ 
sion ignition systems which are used on the 
automobile, aviation, truck and most tractor 
engines. 

Low Tension or “Make and Break” 
Ignition System 

Fig. 236 shows a typical low tension system 
as applied to a one-cylinder four-stroke cycle 
engine. In order that the parts of the ignition 
system may be emphasized, only a few of the 
principal parts of the engine are shown. 

The igniter is a mechanically operated switch 
which opens and closes the circuit within the 
combustion chamber of the engine, so that the 
spark which occurs when the contacts (C) sep¬ 
arate will ignite the mixture compressed in the 
cylinder. (D) is a rod that passes through the 
cylinder wall but is insulated from the plug 
by mica washers. The outer end of this rod is 
the igniter terminal and the inner end is one 
of the igniter contacts. A second rod or shaft 
passes through the cylinder but is made to 
rotate, and on the inner end of this shaft is 
fastened an arm that carries the other igniter 
contact. On the outer end of the shaft is an¬ 
other arm by which the shaft is rotated far 
enough to bring the contact on the inner arm 
against the contact on the inner end of rod 
(D). The contacts are opened and closed by 
the push-rod (J) which is actuated in one di¬ 
rection by the cam (K) on the camshaft and in 
the other direction by the spring (L). 

The coil has one winding on a soft iron 
core. There are only two terminals (A) and 
(B) on the coil, and it is usually about the size 
of a dry-cell. The battery is usually five dry- 
cells connected in series, or ten dry cells con¬ 
nected in series-parallel. One terminal of the 
battery is grounded to the frame of the engine 
at some point as shown, and the other terminal 
connects through the switch to terminal <A) of 
the coil. 

Operation of Low Tension Ignition System 

The ignition switch is first closed. The en¬ 


gine is then cranked. As the piston comes up 
on compression stroke the cam on the cam¬ 
shaft forces the push-rod (,J) up, closing the 
igniter contacts. When the contacts come 
together, the E. M. F. of the battery causes 
current to fiow through the circuit. As the cur¬ 
rent fiows through the coil, the core is mag¬ 
netized and a large number of magnetic lines 
of force are set up, which expand around the 
coil. As the piston continues to move up, the 
cam turns farther so that by the time the com¬ 
pression stroke has been completed, the lobe of 
the cam slips from beneath the push-rod (J) 
and the spring (L) throws the push-rod back, 
causing igniter contacts to be thrown apart as 
nut (F) strikes the igniter arm. 

When the igniter contacts separate, the cir¬ 
cuit is broken and the self-induction of the coil 
causes a strong spark to occur between the 
contacts (C). This spark ignites the gases 
compressed in the combustion chamber of the 
cylinder causing them to explode (rapidly ex¬ 
pand), and drive the piston down, giving a 
power stroke to the engine. 

The cam is driven at half crankshaft speed 
so that when the piston again comes up on 
compression stroke the same series of events 
will be repeated. The spark is always produced 
when the igniter contacts separate, and not 
when they close. 

Low tension ignition systems are simple and 
have a high degree of reliability. On the other 
hand, they are noisy, not flexible enough to give 
a wide range of speed, and the igniter contacts 
soon become burned and pitted, requiring fre¬ 
quent cleaning and smoothing. 

High Tension or “Jump Spark” Ignition 

There are two distinct circuits in a jump 
spark system—primary and secondary. (See 
Fig. 237.) The primary circuit includes a 
source of E. M. F., ignition switch, primary of 
coil, breaker, and a condenser. The secondary 
circuit includes the secondary of the coil and 
spark plug. The wire used to connect the sec¬ 
ondary to the spark plug is well insulated to 
prevent the secondary current from leaping 
from the wire to some metal part of the engine 
before it jumps the gap in the spark plug. 




286 


ELEMENTS OF ELECTRICITY 


Since the voltage in the secondary is very high, 
ranging from 12,000 to 30,000 volts, wire espe¬ 
cially insulated to withstand that voltage is 
called secondary or high tension cable. Be¬ 
cause of the high voltage in the secondary, the 
jump spark system is often called a high ten¬ 
sion system. 

The source of E. M. F. which produces the 
current in the primary may be a battery, 
generator, or magneto. If the system is used 
with a battery, or with the generator used to 
charge a battery, it is called a battery ignition 
system. If a magneto is used to produce the 
current in the primary, the system is called 
a magneto ignition system. 

The induction coil is the same as that de¬ 


scribed under “Induction Coil.” The coil 
transforms the low tension current which a 
battery produces into a high tension current 
of sufficient pressure to drive it across the gap 
in the spark plug. 

The breaker is a mechanically operated 
switch used to open and close the primary 
circuit. The mechanism by which it is oper¬ 
ated is timed to the crankshaft so that the 
spark is produced at the proper time. Because 
the breaker times the spark, it is often called a 
timer; however, this device must not be con¬ 
fused with the device called a timer which is 
used on Ford ignition systems. The breaker is 
also called “interrupter.” 

A condenser is connected in parallel with the 



+ 


A. and B. Terminals of the low tension coil. 

C. Igniter points or contacts. 

D. Igniter terminal. The rod of which the terminal 
is a part is insulated from the cylinder hy mica washers 
and carries one of the igniter contacts. 

E. Camshaft gear. 

F. Nut at top of rod (J). This nut strikes the igniter 
arm when (J) is thrown back by spring (L), causing 
igniter contacts to separate. 

G. Coil spring on (J) placed between the igniter arm 

and shoulder on (J). (G) prevents excessive strain 

being thrown on the igniter mechanism when cam (K) 


forces (J) past the point where igniter contacts come 
together. 

H. Guide for (J). 

J. Push rod. 

K. Cam. This cam is mounted on a shaft with gear 
(E). Gear (E) has twice as many teeth as the gear on 
the crankshaft so turns at half crankshaft speed. The 
gears are so meshed that lobe (K) turns from beneath 
(J) when piston reaches the point where the spark 
should occur. 

L. Return spring for (J). When lobe of cam turns 
from beneath (J), spring (L) forces (J) down. 











































































































IGNITION 


237 


breaker to prevent sparking at breaker points. 
The condenser is sometimes in the coil and 
sometimes in the breaker housing. In either 
case, it is always connected in parallel with the 
breaker. 

Action of the Jump Spark System 

(See Fig. 237) 

When the ignition switch is closed, the E. M. 
F. of the battery causes current to flow through 
the primary of coil while the breaker points are 
together. The current as it flows through 
in the primary magnetizes core, setting up a 
magnetic field about the secondary. When the 


breaker points separate, the current in the 
primary is interrupted causing the held to 
collapse. The strong E. M. F. induced in the 
secondary as the lines collapse, drives the cur¬ 
rent across the gap in the plug, producing 
the spark. 

The secondary circuit, traced from the sec¬ 
ondary of coil, is from secondary terminal 
through high tension cable to spark plug, 
across the gap in plug to the shell, from shell 
to cylinder, through walls of cylinder and 
crankcase to the wire connecting ground termi¬ 
nal of secondary to crankcase, and through the 
wire back to the secondary. 

The gears through which the crankshaft 



FIG. 237 


JUMP SPARK SYSTEM FOR ONE CYLINDER ENGINE 


A. Small screw carrying one of the breaker points. 
It is provided with a locknut to lock it in adjustment. 

B. Breaker arm. The end of the arm carrying the 
breaker point is forced up when lobe of cam (C) turns 
beneath the fiber roller which the arm carries. 

C. Breaker cam which is driven at half crankshaft 
speed. The gears through which it is driven by the 
crankshaft are so meshed that lobe turns beneath the 
roller on breaker arm, separating the breaker points B, 
just as piston passes top dead center between compres¬ 
sion and power strokes. 

D. and F. Primary terminals of coil. 

E. Exhaust cam. 

G. Secondary ground terminal on coil, 

H. and M. Valve timing gears. 

I. Inlet cam. 


J. Secondary ground connection on engine. 

K. Secondary of coil. 

L. Spark advance and retard lever. If this lever is 
thrown to the left as shown by dotted lines in the illus¬ 
tration, the breaker housing is moved around the axis of 
the cam. This pulls the breaker arm around to a point 
where the cam separates the breaker points earlier in 
the rotation of cam and so causes spark to occur earlier. 

P. Breaker points or contacts—usually made of 
tungsten, sometimes platinum. 

PR. Primary of coil. 

PL. Spark plug. 

R. Condenser. 

S. Ignition switch. 

SEC. Secondary terminal of coil which connects to 
the spark plug. 
























































































238 


ELEMENTS OF ELECTRICITY 


drives the breaker cam are so meshed that 
the cam separates the breaker points when 
piston just passes top dead center at the end 
of the compression stroke. If the spark 
lever is moved to the position shown in dotted 
lines, the breaker arm is moved against the 
rotation of the cam and so causes the breaker 


to interrupt the current a little before piston 
reaches top dead center. This gives an ad¬ 
vanced spark which is necessary at higher en¬ 
gine speeds. The retarded spark, as is pro¬ 
duced with spark lever in the position shown 
in solid lines, is necessary when starting to pre¬ 
vent engine from kicking back. 


FIG. 238 



SIX CYLINDER DISTRIBUTOR-BREAKER, CLOSED 
CIRCUIT TYPE—REMY 


A. Distributor brush. Instead of contacts as in 
Fig. 239, pins are molded in distributor bead. These 
pins project through the head and are so placed that 
the end of brush swings past without touching them, 
the gap between pin and brush being about .015". 

B. Cam. The cam is locked on tapered shaft with a 


locknut which is concealed in the figure by the distribu¬ 
tor brush. 

C. Locknut for locking breaker point adjustment. 

D. Breaker points. 

E. Breaker arm. 

F. Spark advance and retard lever. 

G. Distributor pin. 





















IGNITION 


239 


Jump spark systems are silent, reliable, and 
are capable of a wide range of spark advance 
and retard. They are used on all aircraft, 
automobile, and truck internal combustion 
engines, and on most tractor engines and on 
a large number of stationary engines. 

Jump Spark System for Multiple Cylinder Engine 

(See Fig. 240) 

The jump spark system for multiple cylinder 


engines differs in general from the one cylinder 
system in that the breaker cam usually has as 
many lobes as there are cylinders in the engine 
and a distributor is added to distribute the 
secondary current to the different spark plugs. 
The illustration in Fig. 238, and the illustration 
in Fig. 246, show typical six cylinder breakers. 
The cam is driven at half crankshaft speed as 
in the one cylinder system. The gears through 
which the cam is driven are so meshed that a 



SECTION THROUGH A DELCO DISTRIBUTOR 


A. 

Small carbon or metal brush. 

G. 

Clip securing distributor 

head. 

B. 

C. 

Contact button. 

Screw which locks cam (J) on shaft. 

H. 

Breaker housing. 


D. 

Distributor head. 

J. 

Breaker cam. 


E. 

Distributor contact. 

L. 

Spiral gear at bottom 

of breaker shaft which 

F. 

Distributor brush, also called segment brush 
or rotor. 


meshes with gear on shaft (K). 





















































































240 


ELEMENTS OF ELECTRICITY 










































































































































IGNITION 241 


lobe of the cam, (spark lever in retard) separ¬ 
ates the points as a piston passes top dead 
center at the end of the compression stroke. 

Distributor 

The illustration in Fig. 239 shows a sec¬ 
tion through a distributor. The distributor 
brush (F) fits on the end of the cam so that it 
must turn with the cam. As many distributor 
contacts (E) as there are lobes on the cam are 
molded in the bakelite head. The arrangement 
of the distributor contacts is shown in Fig. 
240. An extra, or odd contact, is carried in the 
center. The secondary of coil connects to this 
central contact and the spark plugs to the 
other contacts. With the distributor head and 
brush in position the small carbon brush (A) 
(Fig. 239) forming the center contact, rests 
on the small metal strip at the top of the brush. 
As the brush revolves with the shaft, the small 
metal contact button (B) slides over the dis¬ 
tributor contacts molded in the head, connect¬ 
ing one after the other to the center contact, 
thus switching one of the plugs at a time in the 
circuit with secondary of coil. The brush so 
fits on the end of the cam that contact button 
(B) is on a distributor contact when breaker 
points separate. The distributor head (D) con¬ 
sists of a bakelite body in which distributor 
pins, or contacts (E), are molded. These pins 
are equally spaced about the inside of the dis¬ 
tributor cap and are connected through sec¬ 
ondary cables to the spark plugs. 

The spark plugs are connected to the dis¬ 
tributor contacts, or pins, according to the di¬ 
rection the distributor brush revolves and the 
firing order of the engine. For example (see 
Fig. 240), suppose the piston in number one 
cylinder of a six-cylinder engine is on top dead 
center at the end of compression stroke and 
the firing order of the engine is 1-5-3-6-2-4. 
Wire the contact on which the brush rests, to 
the plug in number one cylinder. Wire the next 
contact in the direction the brush revolves, to 
the plug in number 5 cylinder, the next, num¬ 
ber 3 cylinder, the next, number 6 cylinder, the 
next, number 2 cylinder, and the last to the 
plug in number 4 cylinder. 

Polarity Ignition Switch 

Switch (A) Fig. 240 is so constructed that 
each time it is thrown to “ON” position, the 
current is passed through breaker points in 
opposite direction. This provision is made on 
some systems to prevent the breaker points 
from polarizing. When the current passes 
through the breaker points in one direction 
only, in time, an irregular pit forms in one and 
an irregular cone on the other. This is the 
result of the current carrying bits of metal 
from one point across and depositing it on the 


other, which is called polarization. Reversing 
the current through the points prevents polar¬ 
ization. A switch so constructed to reverse 
(he current is called a polarity switch. A 
polarity ignition switch can almost always be 
connected properly if diagonally opposite term¬ 
inals are connected to the breaker and coil, 
and the other terminals to battery and ground. 

Spark Coil Connections 

(See Fig. 240) 

This coil is of the type designed to be 
mounted .on a metal bracket which bolts,to the 
crankcase or to the frame of the car. One end 
of the secondary connects to a metal contact 
in the base of the coil box. This contact must 
rest on some piece of metal which is grounded 
or no ground connection will be made to com¬ 
plete the secondary circuit. If the coil is 
mounted on a wooden dash, the contact in the 
base must be grounded with a wire. Terminal 
(M) is connected to the battery; terminal (F) 
to the battery and one side of the breaker; 
terminal (K) to the other side of the breaker, 
making the condenser in parallel with the 
breaker points. 

Some spark coils have one end of secondary 
connected to a terminal to which one end of the 
primary connects. Coils of this type are used 
on systems grounding one terminal of battery. 
The ground return for the secondary current 
is then obtained through battery and switch. 

Tests for Coil Terminals 

The terminals of a coil constructed as shown 
in Fig. 240 can be determined .with a test lamp. 
If the test points are placed on the condenser 
terminals (F) and (K), the lamp will not light 
and no spark will occur when the points are 
lifted. The condenser will be charged, how¬ 
ever, and a spark will be produced if it is dis¬ 
charged by touching a short wire to these two 
terminals. 

To distinguish between the primary terminal 
(M) and the primary and condenser terminal 
(K), charge the condenser and note the in¬ 
tensity of the spark produced when the con¬ 
denser is discharged by connecting terminals 
(F) and (M). Charge the condenser again 
and note the spark produced when discharged 
by connecting terminals (F) and (K). The 
weaker spark will occur when connecting 
terminals (F) and (M) since the condenser 
must then discharge through the primary coil 
and ignition resistance. 

The terminals to which the secondary con¬ 
nects can easily be determined with a test 
lamp. The lamp will not light while test 
points are on secondary terminals but a spark 
will be produced at a test point when lifted 
from the terminal. 

The primary terminals can be determined 






:>42 


ELEMENTS 0E ELECTRICITY 


with a test buzzer. A test buzzer sounds a 
little lower when the points are on the ter¬ 
minals of the primary than when the ]mints 
are held together. 

Open Circuit and Closed Circuit Type Breakers 

Open circuit type breakers are so constructed 
that a spring separates the points and a cam 
forces them together. The cam is usually so 
constructed that breaker is open a little longer 
than closed. In the Atwater-Kent open circuit 
type breaker the mechanism is so constructed 
that it is not possible to stop the breaker cam 
so that the points are together. The points 
remain closed just as long at high speeds as at 
low speeds, so the spark at all speeds of engine 
is practically the same. 

In the closed circuit type breaker the spring 
forces the points together and the cam sep¬ 
arates them. (See Figs. 238 and 24G.) The cam 
is usually so constructed that breaker remains 
closed a little longer than open. This is done 



FIG. 241 

REMY IGNITION-DISTRIBUTOR 

to give more time for current to build up in 
primary of coil at high speeds. Since with this 
construction the breaker remains closed longer 
at low speeds than at high speeds, a ballast 
resistance is necessary for the primary circuit 
as shown at (C) Fig. 240. This resistance is 
called the ignition resistance unit. 

Ignition Resistance 

(See Fig. 240) 

At high speeds the breaker remains closed 
for a very short space of time, conse¬ 
quently the coil must be of low resistance, if 
the E. M. F. of the battery builds up current 
strong enough to magnetize the core, while the 
breaker remains closed. If the coil has low 
enough resistance for the E. M. F. of the bat¬ 
tery to magnetize the core at high speeds, the 
resistance will be so low, that at low speeds, 
when breaker remains closed longer, the cur¬ 


rent will reach a strength which will heat the 
coil. To prevent this, the ignition resistance 
unit is connected in series with the primary. 

The ignition resistance is a small coil, usually 
of iron wire, wound on a porcelain spool. 
The wire is of such size that it will safely carry 
the current that will magnetize the core, but 
when the current becomes excessive, as at 
lower si)eeds, the wire becomes heated. As the 
temperature rises the resistance of the wire in¬ 
creases rapidly. This increase in resistance 
I)revents the current from reaching a strength 
that will heat the spark coil and cause spark¬ 
ing at the breaker points. 

The closed circuit type ignition systems can 
sometimes be operated without the ignition re¬ 
sistance, but in doing so the coil is likely to heat 



FIG. 242 

GENERATOR MOUNTING FOR IGNITION- 
DISTRIBUTOR 


and sparking to occur at the breaker points. 
The resistance unit offers further protection to 
the system, as it will burn out before the cur¬ 
rent reaches a strength that would burn out 
the coil. 

When the open circuit type breaker is used, 
it is not necessary to use the ignition resist¬ 
ance, since the breaker remains closed just as 
long at high speeds as at low speeds. The 
primary of some coils is wound of such wire 
that the primary acts both as the ignition re¬ 
sistance and the primary. No resistance unit 
is used with coils of this type. 

Breaker Point Adjustment 

The breaker point adjustment for breakers 
used in battery ignition systems varies with 
the type and make of breaker. Some adjust 
for points to separate only .006" and some ad¬ 
just for points to separate as much as .030". 










IGNITION 


243 


A small wrench, carrying two thickness 
gauges, is usually provided by the manu¬ 
facturers to make the breaker point and spark 
plug adjustment. One gauge should just slip 
between points when fully separated, if prop¬ 
erly adjusted. The other gauge should just 
slip between electrodes of spark plug. Without 
the gauge provided for the particular systems 
on which adjustments are being made, adjust 
according to manufacturers’ instructions. The 
majority of breakers adjust for points to sep¬ 
arate between .012" and .020". 

Spark Plug Gap 

The width of gap in the spark plug varies 
with the type of ignition system and type 


spark must be advanced, since it takes a little 
time for the charge of vaporized fuel com¬ 
pressed in the combustion chamber to burn 
and so expand or explode. If, while engine is 
running, the spark does not occur a little be¬ 
fore the piston passes top dead center, the ex¬ 
plosion will not occur till the piston has moved 
part way down on the power stroke, in which 
case there is a loss in power and the engine is 
abnormally heated. To prevent this the spark 
should be advanced. The charge then begins to 
burn while the piston is at top of cylinder and 
the explosion takes place before piston has 
moved down but very little on power stroke. 

If the spark is advanced too far, the explosion 
takes place before the piston has time to 



FIG. 243 

DELCO AUTOMATIC SPARK CONTROL—ESSEX 


engine on which they are used. The gap in 
spark plugs used in battery ignition systems 
should be, on an average, from .025" to .030" 

Spark Advance and Retard 

When starting an engine, the spark should 
not occur till the piston has reached top dead 
center at the end of the compression stroke. 
If the spark occurs before the piston reaches 
top dead center, the piston is likely to be driven 
back down before having passed top dead cen¬ 
ter, thus causing the engine to kick back. 
After the engine is started and is running, the 


pass top dead center. In this event, when the 
engine is running, the momentum of the fly¬ 
wheel will usually drive the piston past top 
dead center, but a peculiar knock, called a 
“spark knock," is produced. 

In the more common types, the breaker 
housing is so constructed that the breaker 
mechanism can be rotated part way around the 
shaft carrying the cam. Then, to advance the 
spark, the breaker mechanism is turned 
against the direction the cam is driven, and to 
retard the spark the breaker mechanism is 
turned in the direction the cam is driven. 
















244 


ELEMENTS OF ELECTRICITY 


Other breaker mechanisms are so con¬ 
structed that the cam is thrown forward to ad¬ 
vance the spark and thrown backwards to re¬ 
tard the spark. Some of the Delco breakers, 
are constructed in this manner. The housing 
of this type breaker is bolted rigidly to the 
crankcase. The shaft carrying the timing 
gear is hollow and has a spiral slot machined 
in it. The shaft on which the cam is mounted 
has a straight slot machined in it at the bottom 
and fits into the hollow shaft that carries the 
gear. A small pin carried by a collar fitting 
around the hollow drive shaft, passes through 
the spiral slot in the hollow shaft and the 
straight slot in the other shaft. A shifting- 
yoke connected to the spark advance and 
retard lever by a fork, controls the position 


takes care of the spark advance and re¬ 
tard so far as the variation in the speed 
of the engine necessitates it, but because 
an engine does not require the spark to be 
advanced as far when pulling, as when run¬ 
ning idle, most of the mechanisms are con¬ 
structed with a manual control as well as an 
automatic. The harder the engine is. pulling 
the more fuel each cylinder draws in on the 
intake stroke and therefore the higher the 
compression. The higher the compression the 
more quickly a mixture of vaporized gasoline 
and air burns, hence, it is not necessary to in¬ 
troduce the spark into the charge so early. 
The average engine will have a spark knock 
under heavy load if the spark lever is advanced 
to the point at which engine runs well at the 



ADJUSTING NUT 


FIG. 244 

DELCO DISTRIBUTOR-BREAKER—ESSEX 


of the collar. When the collar is moved up¬ 
ward, or downward by the shifting yoke, the 
pin passing along the spiral slot in the hollow 
shaft and the straight slot in the other shaft, 
either throws the cam forward or backward. 
If the cam is thrown forward, the spark is ad¬ 
vanced. If the cam is thrown backward, the 
spark is retarded. 

The automatic spark advance and retard is 
controlled by a governor mechanism. As the 
speed increases, the spark is automatically ad¬ 
vanced, and as speed decreases, the spark is 
automatically retarded. 

The automatic spark advance and retard 


same speed under little load. The range of ad¬ 
vance obtained by the automatic advance is 
independent of the hand advance. The actual 
advance is equal to their sum, expressed in 
degrees. 

The illustration in Fig. 239 shows a sec¬ 
tion through one of the later types of Delco 
ignition-distributors. The distributor brush 
(rotor) makes a wiping contact on the dis¬ 
tributor segments which are molded in the 
distributor head flush with the surface of the 
bakelite. The cam is locked on the shaft by a 
tapered screw that is threaded into the top of 





IGNITION 


245 


the shaft. To change the timing with this type 
of breaker it is not necessary to draw the tim¬ 
ing gears out of mesh as the cam can be loos¬ 
ened on the shaft by loosening the tapered 
screw. 

Fig. 238 shows a Remy distributor-breaker 
and distributor brush. The cam is locked on 


the tapered shaft by a lock nut (not shown 
in illustration). To loosen the cam, remove 
lock nut and pull cam from the tapered shaft 
with a cam puller. The distributor brush does 
not rub against the pins (G) in the distributor 
head, but there should be a gap of about .015 
of an inch between the brush and the pin. 


c 



SIX CYLINDER CLOSED CIRCUIT TYPE BREAKER 
DELCO 


A. Breaker point adjusting nut. • Adjustment for 
opening of points is made here. The adjustment on 
this type is so contacts separate .018" to .020". 

B. Breaker points or contacts, usually made of tung¬ 
sten. 

C. Locknut for (A). 

D. Fiber block carried on breaker arm. The lobes 
of cam strike this block and so separate points. 

E. Lobe of cam. 

F. Wire from coil which connects to plate carrying 
breaker point. A sheet of fiber beneath the plate 
insulates it from the breaker housing. 


G. Spark advance and retard lever. 

H. Breaker arm, grounded through spring (J) which 
rests against breaker housing and through the pin on 
which it is mounted. 

J. Breaker spring which forces points together when 
lobe of cam is not under (D). 

K. Top part of cam on which distributor brush fits. 
One side is cut away a bit more than other so brush 
will fit on cam in one way only. 

L. Tapered screw which locks cam on shaft. See 
(C) in Fig. 239. The cam can be loosened on the shaft 
for timing ignition by loosening this screw. 



















246 


ELEMENTS OP ELECTRICITY 



FIG. 246 


BREAKER MECHANISM USED ON THE PACKARD TWIN SIX 


There are two breakers operated by one cam. Cam 
is driven at crankshaft speed. There are two 6 cyl¬ 
inder distributors, and two coils. One coil, breaker, and 
distributor fire one bank of cylinders and the other coil, 
breaker, and distributor fire the other bank. 

M. Cam. 

N. and O. Breaker arms—not grounded as in Fig. 246. 

P. and Q. Breaker springs. 

R. Gap between points when separated. 


S. Breaker point adjustment. 

T. Locknut. 

U. Breaker points or contacts. 

V. and W. Terminals to which wires from coils con¬ 
nect. 

X. Ignition resistance. 

Y. Screw which grounds one end of each resistance 
coil. 





















































IGNITION 


247 



FIG. 247 

SECTIONAL VIEWS OF TYPICAL SPARK PLUGS 


In center illustration, (C) is the terminal on the upper 
end of the small rod (D) which passes through the 
porcelain core (B). Porcelain is used here because it is 
a very good insulator and at the same time withstands 
heat. Rod (D) must be well insulated from the other 
parts of the plug. Mica washers instead of porcelain 
are sometimes used to insulate this rod. (A) is the 
shell of the plug, or the part that screws into the cylin¬ 
der. (I) is a bushing that holds the core (B) in the 
shell. (E) and (F) are gaskets of copper covered asbes¬ 
tos, placed between the core and the shell and between 
the core and bushing. These gaskets are a seal between 
the core and the shell and at the same time allow for the 
unequal expansion between the porcelain and the metal 
shell, so that as the porcelain heats, it will not crack. 
The gap between electrode (D) and the smaller elec¬ 
trode in the plug base (A) is the gap through which 
the high secondary voltage of the coil drives the elec¬ 
tricity to produce the spark. This gap is inside the 
combustion chamber when the plug is screwed into the 
cylinder. 

The illustration at the left shows a sectional view of 
the one-piece or inseparable type spark plug. The porce¬ 
lain (B) is held into the plug base (A) by means of 
crimping, or rolling the top edge of base (A) over a 
shoulder of the porcelain insulator. Copper-ashestos 
gaskets (E) and (F) serve the same purpose in this 
plug, as in the separable type previously described. 

Spark Plug Bases 

There are three distinct types of spark plug bases in 
common use: the S'. A. E. standard base, the half-inch 
pipe size base and the metric base. 


Two of the S. A. E. standard bases are shown at the 
right. The S. A. E. standard base is % inch in diameter 
across the threads and has 18 threads to the inch. The 
threaded portion of the base is straight and has a 
shoulder above the threads which turns down against 
a copper-asbestos gasket as shown at (G) in left-hand 
illustration. 

Both of the S. A. E. standard bases shown in right 
hand illustrations are identical below the shoulder. 
The only practical differences in the two bases are 
above the shoulder. One of the bases is % inch across 
the flats of the hex, and the other is 1% inch across 
the flats of the hex. 

The half inch pipe size spark plug base is % inch 
across the threads. The threaded portion is tapered in 
the same manner that the threaded portion of 14 inch 
iron pipe is tapered. There are 14 threads to the inch. 

The metric plug differs from the S. A. E. standard in 
that it is .705 inch across the threads. It has 18 threads 
to the inch. 

Spark plugs should always be turned into the cylinder 
firmly, with a wrench, to prevent air leaks around the 
threads. 

Caution 

Never turn a cold tapered spark plug into a hot cyl¬ 
inder as tightly as it will go, but turn it down by hand 
and allow it to become heated, then tighten with wrench. 
If the cold plug is turned in tightly, when it heats it ex¬ 
pands and is liable to seize, making removal very diffi¬ 
cult. Use oil and graphite on threads of spark plugs. 











































































































































MAGNETOS 


Early forms of ignition systems depended 
upon dry cells as a source of E. M. F. but, since 
the dry cells would polarize or become dis¬ 
charged, causing ignition trouble, better igni¬ 
tion systems were demanded. To provide a 
more reliable source of E. M. F. than that offer¬ 
ed by dry cells, magnetos were added to the 
equipment of the automobile. From time to 
time various supplementary parts were added, 
or combined with the magneto until the pres¬ 
ent, highly efficient high tension magneto— 
which is virtually a complete system in itself— 
was developed. Since the addition to the au¬ 
tomobile of the storage battery and a genera- 


causes current to flow through the' loop and 
the lamp in the direction indicated by the 
arrows. When the loop has revolved a quarter 
turn from the position in the illustration, the 
sides of the loop are then moving parallel to 
the lines of force and no E. M. F. is induced in 
the loop, so no current flows. 

When the loop has revolved a little further, 
it begins cutting the lines of force again, but 
the sides of the loop have changed places and 
this time the induced E. M. F. acts to cause a 
current to flow through loop in the opposite 
direction. When the loop has moved another 
quarter turn, the sides of loop are again mov- 



tor to keep it charged, the tendency is strongly 
toward battery ignition systems. However, 
many magnetos are used on automobiles and 
they are very extensively used on trucks, trac¬ 
tors and aircraft engines. 

The fundamental principle of the magneto 
can be obtained from Fig. 248. The rings 
and brushes form slipping connections to the 
ends of the loop, so that the loop can be re¬ 
volved in the field, and still have a connection 
to the lamp (K). As the loop revolves past the 
position shown, it is cutting the magnetic lines 
of force and an E. M. F. is induced in it, which 


ing parallel to lines of force and no E. M. F. is 
induced in the loop. The next quarter turn 
brings the loop back to the position shown in 
figure. 

As the loop revolves an E. M. F. is induced in 
it that builds up to maximum while the sides 
are moving directly across the lines of force 
and drops to zero while sides move parallel 
to the lines of force. Each half turn the E. M. 
F. reverses. 

In the construction of the magneto, instead 
of using a loop, a coil of wire is wound around 
a soft iron core. The core is much the same 

















MAGNETOS 


249 






Ci 



d 


ADVANCE E. RETARD 





















































































































250 


ELEMENTS OF ELECTRICITY 


shape as a shuttle. In Fig. 252 is shown a 
section through an armature of a low tension 
magneto. One end of the coil is grounded to 
the iron core, and other end connects to the 
lead screw which is insulated from the shaft 
through which it passes. To the ends of the 
core are fastened bronze plates in which the 
shafts are secured. These end plates are made 
of non-magnetic material so that the magnetic 
lines of force will not be shunted around the 
core. The core, coil, end plates and shafts 
assembled form the part of the magneto called 
the armature. The armature is mounted in 
bearings at either end of magneto and revolves 
between the poles of the magnets. 

Fig. 249, illustration (A) shows a cross- 
section of a low tension revolving armature 
type magneto. The pieces secured to the 
poles of the magneto are called the “pole 
shoes.” The pole shoes reduce the air gap be¬ 
tween the poles of the magnets and the arma¬ 
ture core. With the armature core in the po¬ 
sition shown at (A) the magnetic lines of force 
set up by the magnets flow from the north 
pole through* pole shoes and core to the south 
pole. The magneto base is of non-magnetic 
material, bronze or aluminum, so that lines of 
force will not flow through it, around the core. 

As the core is revolved, the sides of the coil 
cut the magnetic lines of force set up by the 
magnets and an E. M. F. is induced in the 
coil. Because of the shape of the core and 
the pole shoes, the E. M. F. in the coil does 
not build up as gradually as in the loop re¬ 
volving in the magnetic field shown in Fig. 
248, but builds up in quick strong impulses, 
lasting for only about a twelfth of a turn. 
The illustrations (A), (B), (C), (D) and (E) 
in Fig. 249 show the path of the magnetic lines 
of force with the core in various positions. 

As the core turns from the position (A) to 
the position (B), the magnetic lines of force 
twist with the core, taking the path of low 
reluctance through the part of the core on 
which the coil is wound, from one pole to the 
other. So long as the lines twist with the core 
they are not cut by the sides of the coil and no 
E. M. F. is induced in coil. When the core is 
turned past position (B), the magnetic lines of 
force begin whipping up on the right side and 
down on the left side, so that when the core 
reaches position (C) the lines are flowing 
through the cheeks of the core and not through 
the coil. As the core turns past position (C) 
and to position (D) the magnetic lines of force 
continue to whip up on the right side and 
down on the left side until the lines again flow 
through the part of the core on which the coil 
is wound, as shown at (D). Hence while the 
core turns from position (B) to position (D) 
the sides of the coil are cutting the lines, and 


E. M. F. is induced in it. Since the lines whip 
across the sides of the coil while core is turning 
only about a twelfth of a revolution they cut 
the lines at a high rate inducing an E. M. F. of 
several volts when armature is turned 100 
revolutions per minute, or more. 

After the core reaches position (D) practic¬ 
ally no lines are cut by the sides of the coil un¬ 
til the core turns about five-twelfths of a revo¬ 
lution further. This brings the core to a posi¬ 
tion that is just one-half revolution from posi¬ 
tion (B). As the core passes this position the 
lines again begin to whip across the sides of the 
coil and again an E. M. F. is induced in the coil, 
but this time the E. M. F. acts in the opposite 
direction. 

The comparative strength of the E. M. F. 
induced in the armature for different positions 
of the core is shown in Fig. 250. The dotted 
line shows the two E. M. F. waves (impulses) 
which are produced per turn of the armature 
and that the wave on one-half turn is in the op¬ 
posite direction to the one following it; conse¬ 
quently, the current that flows is an alternating 
current. The curve shown in full lines repre¬ 
sents the comparative strength of current de¬ 
livered by a magneto. The current, because of 
self-induction, lags behind the E. M. F. and so 
does not reach full strength -until the tip of 
core has broken away from pole shoe from 
about 1/64” to 1/16”. 

Connection is made to the ends of the 
armature coil through the lead screw and the 
ground. A small brush or spring is carried in 
the breaker cap of magneto which, when cap 
is in position, rubs against the end of the lead 
screw. A terminal is provided on the cap for 
connection to the brush. On some magnetos a 
collector ring to which one end of armature 
coil connects is placed on the end of the arma¬ 
ture instead of using a lead screw. A terminal 
is then provided on the brush holder which 
holds a small carbon brush on the ring. To 
make a better ground connection to the revolv¬ 
ing core than that made through bearings, a 
small carbon brush which rubs against the end 
of armature is usually carried in one of the end 
plates. 

LOW TENSION MAGNETO 
Revolving Armature Type 

The E. M. F. generated by low tension mag¬ 
netos is seldom more than 30 volts, hence the 
current which it produces is low tension. 
There is only one winding in the low tension 
armature. This winding is usually about No. 
18 insulated copper wire. 

When the low tension magneto is used on 
low tension systems, it is usually the oscillating 
type. That is, instead of the armature making 
complete revolutions, it oscillates through a 





MAGNETOS 


251 


small angle. Heavy coil springs are arranged 
to bring the core to the position shown at “C” 
in Fig. 249. The igniter contacts on the engine 
which connect directly to armature, stand 
normally closed. As the push rod which oper¬ 
ates the igniter is moved out by the cam, it 
rocks the armature core back to position 
shown at (B) in Fig. 249. When the spark 
should occur, the push rod trips and the heavy 
springs throw the core back to vertical posi¬ 
tion. The core does not come to rest when it 
reaches a vertical position but swings beyond 


up through the armature coil as a result of the 
E. M. F. induced in it. Just as the tip of the 
armature core breaks away from the tip of the 
pole shoe (the point when current in coil is 
maximum) the igniter contacts are thrown 
apart breaking the circuit within the combus¬ 
tion chamber. The self-induction of the arma¬ 
ture forces current across the gap between 
contacts as they separate, producing a heavy 
spark which ignites the charge in the cylinder. 

This type magneto is generally used on single 
cylinder stationary engines. 



the vertical position to about the position 
shown at (E), making a few oscillations which 
quickly die out. 

The springs during this operation throw the 
armature through the part of a revolution 
in which the magnetic lines of force cut the 
sides of the armature coil, and so past the point 
at which the E. M. F. is induced. The igniter 
contacts are held together, shorting the arma¬ 
ture coil until the tip of the armature core 
breaks away from the tip of the pole shoe so 
that a comparatively strong current will build 


If the low tension magneto is used in a 
high tension ignition system, an induction 
coil and breaker must be used. A breaker is 
usually carried on the magneto and is timed 
to the armature. The breaker cam is so 
keyed on the armature shaft that the contact 
points separate in full advance just as the tip 
of the armature core breaks away from the 
pole shoe—from 1/64" to 1/16" varying with 
different magnetos—and in full retard when tip 
of core is from 3/8" to 3/4" from pole shoe. 
Fig. 249,. illustration (D) shows position of 





















252 


ELEMENTS OF ELECTRICITY 


core when points separate in full advance with 
armature turning clockwise and illustration 
(E) shows position of core when points sep¬ 
arate in full retard. The timing of the breaker 
to the armature is necessary in order that 
points separate while the current is flowing 
through the coil. The current is about maxi¬ 
mum when points separate in full advance, 
hence the advanced spark is more intense than 
the retarded spark. 

If the magneto is for a multiple cylinder en¬ 
gine it is equipped with a distributor. The 
distributor brush is carried on a large gear that 
is driven by a smaller gear on the armature. 
The distributor brush is always driven at one- 
half crankshaft speed for the four stroke cycle 
engine. 

The relative speeds of the armature and the 
crankshaft depend on the number of cylinders 
in the engine on which the magneto is used. 
If it is a four cylinder engine, the armature is 
driven at crankshaft speed. The large distrib¬ 
utor gear will then have twice as many teeth as 
the small gear on the armature. If it is a 
six cylinder engine, the armature will be driven 
at one and a half times crankshaft speed and 
the large distributor gear will have three times 
as many teeth as the gear on the armature. 
If it is an eight cylinder engine, the armature 
will be driven at twice crankshaft speed, and 
the large distributor gear will have four times 
as many teeth as the small gear on the 
armature. 

Distributor gears must be so meshed that 
the distributor brush will always be on a dis¬ 
tributor segment when the breaker points sep¬ 
arate. The following is an easy way to time 
the distributor gears: 

Place the breaker mechanism halfway 
between full advance and full retard position 
and then turn the armature forward till the 
breaker points just begin to separate. Stop 
the armature and hold it in this position. Draw 
the distributor gears out of mesh and rotate 
the large gear to the position at which the dis¬ 
tributor brush will be in the center of a seg¬ 
ment with the distributor head in position, 
then re-mesh the gears. The gears should 
then be so meshed that, when the breaker 
points separate half way between full advance 
and retard, the distributor brush will be in the 
middle of a segment. 

Fig. 251 shows the breaker and distributor 
end of a low tension magneto. The heavy lines 
show the position of the distributor brush 
when breaker points separate in full ad¬ 
vance. The dotted lines show the position of 
the brush when the breaker points separate 
in full retard. It should be noted that distribu¬ 
tor brush turns in opposite direction to the 
armature. 


The breaker mechanism as shown, is car¬ 
ried in the breaker housing. The cam (C) is 
carried on the shaft. The fixed breaker 
point is insulated from the housing by fibre 
washers, which are shown in black. This 
point is carried on a small bolt that screws 
through the insulated support. The locknut on 
the bolt locks the bolt in position when 
properly adjusted. The other breaker point 
is carried on the breaker arm (A) which is 
grounded. A small spring draws the breaker 
arm down and closes the breaker when the 
lobe of the cam carried on the shaft turns from 
beneath the fibre roller on the arm. The break¬ 
er housing is so attached to the end-plate of 
the magneto that it can revolve part way 
around the shaft as an axis. A small lever is 
attached to the housing with which the hous¬ 
ing is moved to advance and retard the spark. 
To advance the spark, the housing should be 
moved in the direction opposite to that in 
which the shaft turns. To retard the spark, 
the housing should be moved in the same di¬ 
rection as the shaft turns. 

The end plate of the magneto and breaker 
housing are made of either bronze or alumi¬ 
num (non-magnetic materials) to prevent the 
magnetic lines of force from flowing around 
the armature core from one pole of the mag¬ 
net to the other. The large distributor gear is 
made of bronze for the same reason. 

Clockwise and Counter-Clockwise Magnetos 

If the breaker and distributor of a magneto 
are properly timed for the magneto to run in 
clockwise direction they will not be properly 
timed if the magneto is turned in a counter¬ 
clockwise direction. That is to say, if the 
breaker points separate in full advance, just 
as the tip of the core breaks away from the 
pole shoe and the distributor brush has just 
come on to a distributor segment with the 
armature turning clockwise, the breaker points 
will not separate in full advance when tip 
of core breaks away from pole shoe, and 
distributor brush will not have just come on to 
a distributor segment, if the armature is turn¬ 
ing counter-clockwise. For this reason, it is 
necessary to specify the direction that the 
magneto is timed to be driven. If, when look¬ 
ing at the driven end of a magneto, the arma¬ 
ture turns in the direction the hands of a clock 
move, the magneto is called a clockwise mag¬ 
neto. If, when looking at the driven end, 
the armature turns in a direction opposite to 
that of the hands of a clock, the magneto is 
called a counter-clockwise or anti-clockwise, 
magneto. When determining whether a mag¬ 
neto is clockwise or counter-clockwise, always 
consider it from the driven end. 



MAGNETOS 


253 



LOW TENSION DUAL MAGNETO SYSTEM 





































































































254 


ELEMENTS OF ELECTRICITY 


To Determine Direction of Rotation 

The direction a magneto should be driven 
can be determined in the following manner. 
Turn the armature slowly in a clockwise di¬ 
rection till the tip of the armature core is just 
breaking away from the pole shoe. If the 
breaker points are then just separating with 
breaker mechanism in full advance, the mag¬ 
neto is clockwise. If the breaker points do 
not separate in full advance as the tip of the 
core is just breaking away from the pole shoe, 
the magneto is probably counter-clockwise. 
Turn the magneto armature counter-clockwise 
till the tip of the armature core just breaks 
away from the pole shoe. If the breaker 
points are separating in full advance with 
the core in this position, the magneto should 
be driven counter-clockwise. If the breaker 
points do not separate in full advance as the 
tip of the core breaks away from the pole shoe 
with the armature turning in either direction, 
it is probable that the wrong cam has been 
placed on the shaft, or the cam has slipped be¬ 
cause of key being left out, or breaker housing 
is not on the magneto in proper position. 

LOW TENSION DUAL MAGNETO 

The low tension dual magneto is called dual 
because the switch and coil with which it is 
used are so constructed that either a battery 
or magneto may be switched into the primary 
circuit and used as a source of E. M. F. The 
breaker and distributor are used when running 
on either magneto or battery. 

Fig. 252 is a wiring diagram for a low tension 
dual magneto ignition system. The switch is 
usually carried on the coil. The switch arm 
has three positions — “OFF,” “BATT.” and 
“MAG.” The connection between (x) and (y) 
on the switch is permanent. 

Operation on Battery 

With the switch in battery position, the 
battiery, coil, breaker and distributor make 
up a battery ignition system. The armature 
of the magneto does not come into use. The 
battery is usually five dry-cells in series. The 
secondary of the coil connects with a high ten¬ 
sion cable to the middle terminal on the dis¬ 
tributor head. 

The distributor switches the secondary of 
coil in circuit with each plug according to 
firing order of engine, hence distributes the 
secondary current to the plugs. 

Operation on Magneto 

When the switch is thrown to the magneto 
position, the battery is disconnected and the 
magneto armature is switched in series with 
the primary of the coil, and the breaker 
in parallel with the primary winding. The 


breaker is so timed to the armature that the 
points are always closed as the E. M. F. builds 
up in the armature. The breaker being 
in parallel with the primary, shorts the arma¬ 
ture when the points are together. Since the 
resistance of the complete armature circuit is 
very low when the breaker is closed, a com¬ 
paratively strong current is built up in the 
armature coil as its sides cut the lines of force 
set up by the magnets. 

At the instant the current in the armature 
reaches about its maximum strength, the 
breaker points separate. When the breaker 
points separate, the circuit is then through the 
primary coil only and all the current which 
fiows through the armature must flow through 
the coil. The high self-induction of the arma¬ 
ture tends to drive the current through the 
primary winding at the same rate that it was 
flowing through the breaker. This results in 
the building up of current through the primary 
at a very high rate, which so quickly mag¬ 
netizes the core that strong enough E. M. F. 
is induced in the secondary to produce the 
spark at the plug. The coil operates by the 
building up of the field when running on mag¬ 
neto, instead of by the collapse of the field, but 
the spark occurs when breaker points separate, 
and when a partial collapse of the lines of force 
is produced in the armature. 

Connecting the breaker in parallel with the 
primary reduces the sparking at the breaker 
points. If both armature and primary of coil 
are connected in series with breaker, the 
sparking at the points is excessive. 

The condenser may be in either the coil or 
the magneto. In either case, it is connected in 
parallel with the breaker. 

Some low tension magnetos carry a con¬ 
denser and coil beneath the arch of the mag¬ 
nets. The coil is connected in the same man¬ 
ner with relation to the magneto, as the coil 
in the low tension dual system, when the 
switch is in “MAG” position. That is, the 
breaker points are connected in parallel with 
the primary of the coil, and a condenser in 
parallel to breaker points. Since the coil is 
mounted within the magneto, the connections 
are made inside and are very well protected. 
The breaker cap carries a terminal which 
makes connection to the armature when cap 
is in position. Connection is made from this 
terminal to one terminal of the ignition switch. 
The other terminal of the ignition switch is 
grounded. When the switch is in “OFF” posi¬ 
tion, it shorts the breaker points. With the 
breaker shorted, the current in the armature is 
not switched to the primary of the coil when 
they separate, therefore any E. M. F. induced 
in the secondary is not strong enough to drive 
the current through the gap in the plug to pro- 




MAGNETOS 


255 



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256 


ELEMENTS OF ELECTRICITY 


diice a spark. When the switch is in “ON” 
position the short on the breaker is broken, 
and the magneto operates the same as a 
low tension dual with the switch in “MAG” 
position. 

An example of the magneto just described 
is found in the Kingston. This magneto 
from outside appearances is much the same 
as a straight high-tension magneto. In¬ 
stead of making connections to the arma¬ 
ture through the lead screw, a small brass 
ring is mounted on a Bakelite spool at the 
driven end of armature, and to this ring, 
one end of the armature winding connects. A 
small carbon brush which rides on the ring 
is carried by the brush holder on the side of 
the end plate of magneto. From this brush 
holder a wire runs to one end of the prim¬ 
ary of coil, one terminal of condenser, and 
to the insulated breaker contact. There is no 
center terminal on the distributor head, since 
connection is made from the secondary coil to 
the distributor, by an insulated shaft that 
passes through the center of the distributor 
gear. 

HIGH TENSION MAGNETO 

Fig. 253 shows a breaker and distributor 
end of a high tension magneto of the revolving 
armature type, and also a longitudinal section 
through the armature. 

There are two windings on the armature 
core, primary and secondary. The pri¬ 
mary (1) is a winding of about No. 20 
insulated copper wire of only a few hun¬ 
dred turns. One end of this winding 
grounds to the core and the other end connects 
to the lead screw (L). In the illustration the 
primary is shown as being wound over just one 
end of the core, but in practice the primary is 
wound from one end of the core to the other 
and usually consists of about four layers. It 
is shown in this manner in order that the cir¬ 
cuits can be traced with greater ease. The 
secondary (2) consists of several thousand 
turns of fine wire usually enamel insulated and 
wound directly over the primary. One end of 
the secondary connects to the end of the pri¬ 
mary that connects to the lead screw and the 
other end of the secondary connects to the col¬ 
lector ring (R) which is carried in the bakelite 
spool at the driven end of the armature. In 
some magnetos the collector is at the breaker 
end of the armature directly under the 
distributor head. There are high flanges 
on both sides of the ring to prevent the 
secondary current from jumping from the 
ring to the ring housing. A condenser (3) 
is carried in the wide end plate of the arma¬ 
ture. The breaker mechanism is mounted on 
a disc that revolves with the armature. The 


cams (I) and (V) are carried in the breaker 
housing. With this construction the primary 
circuit is completed in the armature and the 
low tension current does not flow through any 
slipping contacts. 

A small carbon brush (B) which rides on the 
collector ring (R) is carried in a fibre or hard 
rubber brush holder (H) that screws into the 
ring housing. From the terminal at the top 
of the brush holder, connection is made with a 
device called a pencil (P) to the distributor 
(X). The pencil passes through the center of 
the distributor gear. The pencil is well insu¬ 
lated at the point where it passes through the 
gear to prevent the secondary current from 
jumping from the pencil to the gear. An in¬ 
duction coil is not necessary for the operation 
of the high tension magneto, since the strong 

E. M. F. which produces the spark at the plug 
is produced in the armature. 

Operation of the High Tension Magneto 

The operation of a high tension magneto 
is in many respects the same as that of a high 
tension induction coil. It differs fundament¬ 
ally in that the E. M. F. causing current to flow 
through primary is generated by causing the 
turns of primary to cut lines of force set up 
by permanent magnets. 

The armature of the revolving armature type 
high tension magneto is revolved between the 
poles of the magnets in the same manner as in 
the armature of the low tension magneto. The 
armature core is of soft iron and of the same 
shape as that in the low tension magneto. 
As the armature is revolved in the field, the 
magnetic lines of force set up by the magnets 
are cut by the sides of the coils, and so in¬ 
duce an E. M. F. in the coils. There are many 
thousand turns in the secondary but it is 
not practical to revolve the armature at a 
speed that would generate in the secondary 
an E. M. F. strong enough to produce a spark 
in the gap of the spark plug, hence the primary, 
condenser and breaker are necessary. 

The breaker, as on the low tension magneto, 
is so timed to the armature that the points are 
together, shorting the primary as the E. M. 

F. is induced in it by its sides cutting the lines 
of force set up by the magnets. The resistance 
being low, a comparatively heavy current is 
generated in the primary, which magnetizes 
the core much stronger than it is magnetized 
by the magnets. Just as the tip of the core is 
breaking away from the pole shoe (the time 
when the current is about maximum in the 
primary) the breaker points separate, inter¬ 
rupting the current. This causes the lines of 
force set up by the current to quickly collapse 
across the secondary at a rate that induces in 
it an E. M. F. strong enough to drive the cur- 






MAGNETOS 


257 


rent across the gap in the plug, producing a 
spark. 

When running with an advanced spark, the 
breaker points separate before the sides of 
the coils have cut all the lines of force set 
up by the magnets. Consequently, because 
of the generator action of the secondary re¬ 
volving in the field set up by the magnets, 
there is still an E. M. F. in the secondary after 
the lines set up by the current in the primary 
have collapsed. This E. M. F., called “follow¬ 
up” voltage, increases the flow of electricity 
through the gap in the plug for an in¬ 
stant after the spark is established, thus 
producing a very intense flame. This peculiar 
“follow-up” voltage produced in the secondary 
of a magneto armature, even though it is of 
very short duration, enables the magneto to 
give a more intense spark than that which is 
produced by battery ignition. 


is fastened to the top of the pole shoes, 
is connected between the secondary terminal 
on the brush holder and the ground. The gap 
is usually set at approximately 5/16". This 
gap is provided to prevent the voltage from ris¬ 
ing high enough in the secondary to puncture 
the insulation on the secondary coils. The 
width of the safety gap is such that its resist¬ 
ance is greater than that of the spark plug and 
yet small enough to protect the secondary coil 
from an excessive voltage that would damage 
it. Sparking at the safety-gap is an indication 
of too wide a gap in the spark plug, or a wire 
disconnected from either the distributor or 
from a spark plug. 

INDUCTOR TYPE MAGNETO 

In the revolving armature type magneto, the 
armature coils are revolved to cause them to 
cut the lines of force. In the inductor type 



FIG. 254 

ROTOR FOR 2, 4 AND 6 CYL. DIXIE MAGNETOS 

N and S. Rotating poles. B. Bronze block to which poles are riveted. 


The condenser carried in the armature is 
connected in parallel with the breaker points 
to prevent sparking between them as they 
separate. The breaker cap carries a small 
spring that presses against the lead screw 
when the cap is in position. Connection is 
made from this spring to the terminal on the 
cap. This terminal connects with a wire to the 
ignition switch. With the switch in “OFF” 
position it grounds the lead screw, shorting the 
breaker points. With the switch in “ON” posi¬ 
tion it is open and so breaks the ground 
connection on the lead screw. The small car¬ 
bon brush (A) carried in the base of the mag¬ 
neto, rubs against the wide end-plate of the 
armature, forming a better connection between 
the base of the magneto and the revolving core 
than could be made through the bearings. 
This gives a better ground connection to 
the primary. Sometimes this brush is car¬ 
ried in the disc which carries the breaker as 
shown at (M) and as the disc revolves with the 
armature the brush rubs against the end-plate 
that carries the bearing. 

The safety gap (Z) on the cover plate which 


magneto the armature coils are stationary and 
the magnetic lines of force are switched 
through the coils in flrst one direction and 
then another. As the lines of force are 
switched through the coil in one direction and 
then in the opposite direction they are cut by 
the sides of the coils and so induce E. M. F. in 
them. Since the coils do not revolve no lead 
screw or collector ring is used. 

DIXIE MAGNETO 

Fig. 255 illustrates the magnetic path as 
formed in the “Dixie” magneto, and the po¬ 
sition of the armature coils with relation to the 
magnets. Rotating poles (N and S) are car¬ 
ried on the drive shaft (Fig. 254) and are 
coupled together by a bronze block (B) to 
which they are riveted. Bronze being non¬ 
magnetic, the magnetic lines of force follow 
the armature core from one pole to the other 
instead of flowing directly from one pole to 
the other through the block to which they are 
riveted. 

The rotating poles form a “magnetic switch” 
which, as they are turned, switch the magnetic 



































258 


ELEMENTS OF ELECTRICITY 


lines of force through the armature coils first 
in one direction and then in the opposite di¬ 
rection. As the lines of force are switched 
back and forth through the coil they are cut 
by the coil and so induce E. M. F. in it. The 
maximum voltage is generated in the primary 
as the rotating poles are passing between the 
ends of the armature core. The current in 
the primary of the armature reaches about 
maximum strength when the rotating pole has 
broken away from the tip of the core .020". 
The Dixie magneto is a high tension magneto 
and so has both primary and secondary arma¬ 
ture windings. 

Since the armature coils do not revolve, the 
breaker is mounted in the housing as in the 


brush that is carried in a cup at the end of an 
insulated rod passing through the distributor 
gear shaft. This insulated rod connects to 
the metal distributor brush that is carried on 
the distributor gear. 

The two magnets fit on either side of the 
rotor shaft instead of straddling the rotor as 
magnets of the revolving armature type 
straddle the armature. 

The breaker cam is keyed on the rotor shaft 
so that the breaker points separate as the rotat¬ 
ing poles break away from tips of the armature 
core .020". The breaker housing is carried on 
a sleeve on which the armature is carried. 
When the breaker housing is moved forward 
to retard the spark, the armature is moved 


FIG. 255 



low tension magneto of the revolving armature 
type. The cam is carried on the shaft, and 
there is no lead screw. One end of the primary 
winding is grounded to the core, the other end 
connects to one terminal of the condenser, and 
to the stationary breaker point. The other 
terminal of the condenser grounds to the core, 
and the breaker point on the breaker arm 
grounds to the breaker housing. 

One end of the secondary is grounded and 
the other end connects to a contact on the side 
of the armature. This contact on the side of 
the armature rests against a small carbon 


forward an equal distance, hence the breaker 
contacts always separate when tip of pole 
breaks away from tip of core .020". The ad¬ 
vantage of this arrangement is that the break¬ 
er points separate at the point when the cur¬ 
rent is maximum in the primary so that maxi¬ 
mum number of lines of force collapse across 
the secondary. The magneto gives a spark of 
equal intensity in both retard and advance. 

The terminal on the breaker cap which con¬ 
nects to the ignition switch, makes connection 
with the stationary breaker point. When the 
ignition switch is thrown to "OFF” position, it 













































MAGNETOS 


259 


grounds this terminal, thus shorting the 
breaker points. 

The four and six cylinder Dixie magnetos 
give two sparks per turn of the rotor just as the 
shuttle type armature magneto, and so there 


pulses of current produced per turn of the rotor 
are used. If the magneto is used for eight or 
twelve cylinders, a four lobe cam is used for the 
breaker, and all four impulses of current are 
used. Since the armature coils do not revolve, 



FIG. 256 


are two lobes on the cam. The rotor for the 
eight and twelve cylinder magnetos has four 
rotating poles instead of two, and so four 
sparks are produced per turn of the rotor. The 
breaker cam on these magnetos has four lobes. 

K-W MAGNETO 

Fig. 257 shows the magnetic circuit of the 
“K-W” magneto. The armature coils are con¬ 
centric with the rotor shaft and are situated 
between the rotating poles or inductors. (See 
Fig. 256.) The opening of the coil is large 
enough for the rotor to turn with the coil held 
stationary. Since this magneto is made in 
both low tension and high tension types, there 
may be one winding or two windings in the 
armature. 

Turning the rotor causes the magnetic lines 
of force to be switched through the arma¬ 
ture coils first in one direction and then in the 
other. As the lines of force are switched 
back and forth through the coil they are 
cut by the sides of the coils and so in¬ 
duce an E. M. F. in them. Four impulses of 
current are produced per revolution of the 
rotor. If the magneto is for a four or six 
cylinder engine there are only two lobes on the 
breaker cam, and only two of the four im- 


the breaker contacts are carried in the breaker 
housing, and the cam is carried on the shaft. 
The breaker points separate in full advance 
just as an inductor breaks away from the pole 
shoe. 














































260 


ELEMENTS OF ELECTRICITY 


TEAGLE MAGNETO 

Figs. 258 and 259 show the magnetic cir¬ 
cuit of the Teagle magneto. This magneto is 
a departure from the conventional type. Bar 
magnets are used instead of horse-shoe mag¬ 
nets and a soft iron base is used instead of a 
bronze or aluminum base. 

By comparing the two diagrams, it can be 
seen how turning the rotor (B) causes the 
lines of force to be cut by the armature coil, 
and so induce an E. M. F. in it. The magneto is 
a high tension magneto, hence there are both 
primary and secondary windings on the arma¬ 
ture. The breaker points separate in advance 
when rotor breaks away from leg of core on 
which the armature coils are wound. 


The duplex coil is much the same as a sub¬ 
stantially constructed buzzer (see Fig. 306). 
A condenser is connected around the vibrator 
contacts of the duplex coil. 

When the ignition switch is thrown to 
the battery position, the battery, duplex coil 
and armature terminal are thrown in series. If 
the magneto breaker points are opened the 
circuit is completed from the armature ter¬ 
minal through the primary winding of the 
armature to the ground, and through the 
ground back to the grounded terminal of the 
battery. As soon as this connection is made, 
the E. M. F, of the battery causes current to 
flow through the circuit. As the current flows 
through the circuit, it magnetizes the core of 
the duplex coil and magnetizes the armature 




HIGH TENSION DUPLEX MAGNETO 
(Vibrator Type) 

Fig. 260 is wiring diagram for a high 
tension duplex magneto. In addition to the 
magneto, which is the same as a straight high 
tension magneto, either revolving armature 
or inductor type, a duplex coil is switched 
in series with a battery and the armature term¬ 
inal on magneto (terminal on breaker cap) 
when switch is in “BAT” or “START” position. 


core. When the current reaches about lyo 
amperes, the core of the duplex coil is magne¬ 
tized strong enough to draw the contacts 
apart. When the contacts separate, the current 
through the circuit is interrupted. The inter¬ 
ruption of the current through the primary 
causes the lines of force to collapse and cut the 
secondary, and so induces in the secondary a 
strong E, M. F. that drives the current across 
the gap in the plug producing a spark. As 





































































MAGNETOS 


261 


soon as the current is interrupted, the core of 
the duplex coil demagnetizes, and the vibrator 
spring throws the contacts together again. 
When the contacts come together the E. M. F. 
of the battery again causes current to build 
up through the primary circuit, repeating the 
operation. As long as the breaker points of 
the magneto are open, a shower of sparks 
is produced at the plug. If the magneto is 
turned so that the breaker points are together, 
the current which the E. M. P. of the battery 
causes to flow, is shorted around the primary 
of armature, hence no sparks are produced at 
the plug. 

When the switch is thrown to “MAG” posi¬ 
tion, the connection between the duplex coil 
and the armature is broken, and the magneto 
runs as a straight high tension magneto. When 
the switch is thrown to the “OFF” position, the 


Fig. 266 shows the breaker mechanism for 
the Bosch high tension dual. There is a re¬ 
volving breaker mechanism for the magneto, 
which is much the same as the breaker mech¬ 
anism for the straight high tension magneto 
revolving armature type, and mounted in the 
lower part of the breaker housing is another 
breaker mechanism which is called the battery 
breaker. It is controlled by a cam carried just 
back of the magneto breaker mechanism. With 
the exception of the double breaker mechanism 
and the absence of a pencil, the high tension 
dual magneto is of practically the same con¬ 
struction as the straight high tension magneto. 

An induction coil is carried in the coil-box 
with the ignition switch. This coil is a high 
tension induction coil, having a core, a primary 
and a secondary winding. A condenser is with¬ 
in the coil box. This coil is used in connec- 



armature terminal is grounded, shorting the 
breaker points. 

The advantage of the duplex pver the 
straight high tension magneto is, a shower of 
sparks can be produced as long as breaker 
points are open, without turning the mag¬ 
neto. This makes starting easier. It is often 
possible to start on the spark, in which case 
it is unnecessary to crank the engine. This, 
however, is only possible when a charge of gas 
is left compressed in one of the cylinders and 
the breaker points are separated. 

Fig. 261 is a combined internal and external 
wiring diagram of the single spark duplex 
system. 

HIGH TENSION DUAL MAGNETO 

Figs. 262 and 264 show high tension dual 
magneto ignition systems. Fig. 262 is the 
Eisemann magneto, and Fig. 264 is the Bosch. 


tion with a battery and the battery breaker 
mechanism on the magneto, when the ignition 
switch is in battery position. The secondary 
of the coil is then connected to the middle 
terminal on the distributor head. The lead 
screw is grounded by the switch so that 
the magneto breaker points are shorted. 
With the switch in this position (“Batt.” posi¬ 
tion) the battery, induction coil, battery break¬ 
er on magneto, magneto distributor and spark 
plugs, form an ignition system, which is used 
for starting. The condenser carried with the 
coil is then in parallel with the battery break¬ 
er points. When the switch is thrown in the 
magneto position, the connections between the 
battery and the coil and between the distribu¬ 
tor and the coil are broken. The secondary of 
the magneto is switched in series with the 
distributor and the ground on lead screw is 
broken. The magneto then runs as a straight 



























262 


ELEMENTS OF ELECTRICITY 



























































MAGNETOS 


263 


high tension magneto. When the switch is 
thrown to “OFF position, the lead screw is 
grounded, shorting the breaker points. 

Fig. ^63 shows the switch terminals and 
switch connections with switch in the various 
positions for the Eisemann. Fig. 265 shows 
the switch terminals and switch connections 
for the Bosch. 


of the magnets are placed together. Fig. 267, 
illustration (A) shows the arrangement of 
magnets on the flywheel. 

The soft iron pieces placed over the poles 
of the magnets form the pole pieces. The 
poles of the magnets are held out from the 
rim of the flywheel by non-magnetic spools, 
and the screws by which the poles are secured 






FORD MAGNETO to the wheel are bronze. The screws which 

The Ford magneto is quite unlike other extend through the flywheel are riveted on the 
types. Instead of using two or three horseshoe back side. The non-magnetic bolts and sup- 
magnets, the Ford magneto has sixteen mag- ports are provided to prevent the magnetic 
nets arranged in a radial manner with their lines of force from flowing from one pole 
poles pointing outward and all bolted to the through the flywheel to the other pole. The 
front of the flywheel of the engine. Like poles shape of the flywheel permits the loop of 

















































































264 


ELEMENTS OF ELECTRICITY 


the magnets to be bolted directly to it. The 
bolts which pass through the loop of the mag¬ 
nets are prevented from working loose by a 
small wire which is passed through the hole 
in the head of each bolt. 

Mounted directly in front of the magnets is 
the armature which is bolted to the crankcase. 
The armature frame is of cast iron and carries 
16 coils about its circumference, so spaced as 
to correspond with poles of the magnets. 

-- —^ /- 


Fig. 268 illustrates the arrangement of the 
coils, and the manner in which they are con¬ 
nected together. One end of the armature 
winding is grounded to the frame as Miown at 
(F), the other end is carried on a small fibre 
block (D) jto the top of the armature. 

The magneto terminal post is mounted on 
the upper half of the flywheel housing, and is 
so mounted that when the flywheel housing is 
in place, the lower end of terminal post rests on 



Bat. 




By means of metal shims between the arma¬ 
ture and the crankcase, adjustment is made on 
the armature so that the coil cores are just 
1/32" in front of the poles of the magnets. The 
armature coils are wound of copper ribbon. 
Eight of these coils are wound in one direction, 
and the other eight in the opposite direction! 


the end of the winding that is carried on the 
fibre block at the top of the armature frame. 
This post is the only terminal on the magneto, 
the other end of armature being grounded. 

As the magnets revolve with the flywheel, 
the magnetic lines of force are cut by the sides 
of the coils and an E. M. F. is induced in them. 






















































MAGNETOS 


265 



FIG. 266 


Air A inch. 



W= y\/ire lock. 

A/= north j^oles. 
5= south poles- 
P= jDoie bieces. 

FIG. 267 




















































266 


ELEMENTS OF ELECTRICITY 


The E. M. F. is induced in the coils while the 
poles of the magnets are moving from one coil 
core to the next, but when the poles are just 
passing the coil cores, the E. M. F. in the coils 
drops to zero, then starts to build up in the 
opposite direction, since the lines of force 
change from cutting one side of the coils to 
cutting the opposite side. This causes the E. 


using a single coil and a distributor, a coil for 
each cylinder is used. The conventional type 
breaker is not used since, if it is timed to mag¬ 
neto, the spark could not be advanced or 
retarded. Instead, each coil is provided with a 
vibrator to interrupt the current in primary, 
and a device called a timer or commutator 
is used to switch each of the coils into circuit 



FIG. 268 


A. Frame. 

B. Coil core. 

C. Coil. 

M. F. to reverse 16 times during a revolution 
of the flywheel, and the current which flows 
as a result of this E. M. F. is an alternating 
current. The magneto is a low tension mag¬ 
neto. 

FORD IGNITION SYSTEM 

The complete Ford ignition system is shown 
by wiring diagram in Fig. 271. Instead of 


D. Armature terminal. 
F. Armature ground. 


with battery or magneto at the proper time. 
Fig. 269 shows diagrammatically the con¬ 
struction of the Ford coil. The core (J) of the 
coil is a bundle of soft iron wires. The primary 
(C) is wound in two layers over the core. One 
end of the primary connects to metal contact 
(B) on the bottom of the wooden coil box. 
The other end of primary connects through the 
vibrator to the upper contact (G) on the side 













MAGNETOS 


267 


of coil box. The secondary connects to the 
two contacts (G) and (M) on the side of coil 
box. The condenser is separated from the coil 
by a glass plate. It is connected in parallel to 
the vibrator contacts. 

The vibrator spring is a flat steel spring 
secured at one end to support (D). The other 
end, which is suspended over the end of core, 
carries a tungsten contact which is held 
against the other tungsten contact at (E). As 
the core is magnetized it attracts the vibrator 
spring, drawing the contacts apart, thereby 


Fig. 273 shows a test arrangement for test¬ 
ing a Ford coil to determine if the vibrator 
spring has the proper tension. If the coil draws 
more than amperes the tension of spring 
is too strong. The tension of spring can be re¬ 
lieved by turning back on small screw (P) so as 
to slightly separate the ends of the horseshoe 
shaped support for the vibrator spring. If the 
coil draws less than 11/2 amperes the spring is 
too weak. Adjustment can be made by turning 
down on the small screw permitting the ends of 
the horseshoe shaped support to spring to- 


^ 

rr fii-^ 



MAG. 


FIG. 269 


breaking the primary circuit. When the core 
is demagnetized the spring again closes the 
contacts. 

There are two adjustments on the vibrator. 
The adjustment at lock-nut (L) is for the 
distance the vibrator contacts separate. This 
adjustment should be made so that the vibra¬ 
tor contacts are .030" apart when the vibrator 
spring is held down against the core. The 
other adjustment, made with the small screw 
(P), is for the tension of the vibrator spring. 
The tension of the spring should be so adjusted 
that the coil draws about 11/2 amperes. 


gether and so throw the vibrator contacts 
together with more force. If the support will 
not spring together enough to give the proper 
amount of tension to the vibrator spring, the 
support should be bent together. To obtain 
access to this small adjusting screw (P), it is 
necessary to remove the small screw directly 
above it with which the spring is secured to the 
support. 

On some of the new coils this type support 
is not used for the vibrator spring. Instead of 
making adjustment here by the small adjust¬ 
ing screw it is necessary to bend the support 

































































268 


ELEMENTS OF ELECTRICITY 


slightly to increase or decrease the tension 
of the spring. 

The fundamental construction of the timer 
is shown in Fig. 271. There are four steel 
segments equally spaced around the inside of 
the timer housing and well insulated from the 
metal shell. Terminals are provided for connec¬ 
tion to each of these segments. A small steel 
roller which is carried on an arm that is pinned 
on the front end of the camshaft, revolves 
within the timer housing. In some of the 
timers a brush is used instead of a roller. This 
brush, or roller, grounds through the camshaft. 
The timer housing fits on over the end of the 
camshaft, just in front of the gear hous¬ 
ing, and is held in position by a metal clip. 


coil box are small brass springs, so spaced that 
the springs press against the contact termin¬ 
als on the coils when the coils are assembled 
in the box. The springs connect to the 
terminals on coil box. The upper row of four 
terminals on coil box connect to timer seg¬ 
ments. The lower row of four terminals con¬ 
nect directly to the spark plugs. The lower 
right hand terminal, looking from front of 
car, connects to the magneto. The lower left 
hand terminal connects to a battery whenever 
a battery is used as an auxilliary source of 
E. M. F. for ignition. 

Operation of Ford Ignition System 

When the switch is thrown to “MAG” po- 



GRCCN -4 
0«.Ut -3 
«e.o - a 
8laC«i 


FIG. 270 


The mounting of the housing permits it to be 
swung around camshaft either in the direction 
in which the roller revolves, or in the direction 
opposite to that in which the roller revolves. 

A small lever is riveted to the metal shell of 
the timer which connects with small rods to 
the spark lever on steering column. By mov¬ 
ing the spark lever down the +imer housing is 
swung around the shaft in the direction oppo¬ 
site to that in which the roller revolves. This 
advances the spark. Moving the spark lever 
up moves the timer housing around the shaft 
in the direction in which the roller revolves. 
This retards the spark. 

The four spark coils are assembled in a coil 
box which carries the terminals. Within the 


sition, magneto, coils, and timer are thrown 
in series. When the timer roller rolls on a 
timer segment, a circuit is completed from the 
magneto terminal through one of the coils and 
the timer to the ground, and through the 
ground back to the magneto armature. The 
E. M. F. generated in the armature of the mag¬ 
neto causes current to flow through the circuit. 
The vibrator on coil interrupts the current 
through the primary as soon as it magnetizes 
the core, and so causes the lines of force 
to collapse across the secondary, inducing 
in the secondary the strong E. M. F. that 
drives the current across the gap in the plug 
to produce the spark. Since the current 
through the primary is interrupted by a vibra- 







































FORD IGNITION SYSTEM 


269 


tor, a shower of sparks is produced at the 
plug connected to the coil in operation, so long 
as timer roller is on the segment. As soon 
as roller rolls off the segment, the coil is 
switched out of the circuit. When the roller 
rolls on another segment, another of the coils 
is switched in circuit with magneto and so is 
thrown into action. The timer controls the 
time of operation of the coils. 

The Ford engine is a four cylinder engine, 
and of the four stroke cycle type therefore a 
cylinder fires every half revolution of the 


this being the firing order of the Ford engine. 

Fig. 270 shows the correct relationship of 
the different parts of the standard Ford ignition 
system. 

Fig. 329 shows the relationship of the cir¬ 
cuits of the standard Ford ignition system to 
the circuits of the starting and lighting system 
on the later models of Ford cars. 

IGNITION TIMING 

Turn the engine forward till the piston in 
No. 1 cylinder moves up to top dead center at 


Green. 



FIG. 271 


crankshaft. Since the camshaft is driven at 
half crankshaft speed, the timer roller makes 
one-fourth of a revolution while the crankshaft 
makes a half revolution. Every one-fourth 
revolution of the roller, the timer switches the 
current through another coil causing another 
cylinder to fire. Connection is made from the 
timer segments to the four upper terminals 
of coil box, so that the coils are switched into 
operation in the following lorders: l-2-4^3, 


the end of compression stroke. Place breaker 
mechanism in full retard. Loosen the breaker 
cam by drawing drive gears out of mesh—or, if 
possible, loosen cam on shaft — and turn it 
in the direction it is driven until the distributor 
brush will be under No. 1 segment in distribu¬ 
tor head when breaker points are just begin¬ 
ning to separate. Mesh the drive gears 
with the cam in this position or lock the cam 
on the shaft in this position. Replace distrib- 














































270 


ELEMENTS OF ELECTRICITY 




FIG. 273 





































































































































SUMMARY 


271 


utor brush and distributor head. Wire the 
segment under which the brush rests to the 
plug in No. 1 cylinder. Wire the other dis¬ 
tributor segments to the plugs in the other 
cylinders according to the firing order of the 
engine and the direction the distributor brush 
revolves. 

Timing With Magneto Ignition 

Turn the engine forward till the piston in 
No. 1 cylinder comes up to top dead center 
at the end of the compression stroke. Place 
the breaker mechanism of the magneto in 
full retard position by turning the breaker 
housing as far as it will go in the direction the 
armature turns. Turn the magneto slowly in 
the direction it is driven until the distributor 
brush comes under No. 1 segment of the dis¬ 
tributor head and the'breaker points are just 
beginning to separate. Couple the magneto 
to the engine with armature in this position 
and then secure the magneto to its sup¬ 
porting bracket. Wire the segment under 
which the distributor brush rests to the 
plug in No. 1 cylinder. Wire the other seg¬ 
ments to the plugs in the other cylinders ac¬ 
cording to the firing order of the engine, and 
the direction the distributor brush revolves. 


Fig. 272 illustrates the method of timing the 
magneto and the method of wiring the dis¬ 
tributor to an engine having a firing order of 
1-3-4-2. 

The timing of Ford ignition is very simple 
so long as the wires to the timer segments are 
connected in the proper order. So long as the 
valves are in proper time the ignition is likely 
to be in time, since the timer roller is carried 
on the camshaft. There are only two positions 
in which the timer roller can be fastened on 
the camshaft. The proper position can be 
determined in the following manner: Turn the 
engine until the piston of No. 1 cylinder comes 
up to top dead center at the end of compression 
stroke. Pin the timer arm on camshaft so 
the roller is on upper left hand segment of 
timer when observed from front of engine. If 
the ignition spark is too early as indicated by 
inability to retard the spark far enough to pre¬ 
vent the spark knock when engine is pulling 
at low speeds, the small rod which connects 
to the lever on timer housing should be 
lengthened. If the ignition spark is late 
this rod should be shortened. With the spark 
lever in full retard the timer roller should not 
roll on timer segment until piston comes up to 
top dead center. 


SUMMARY 


MAGNETISM 

Magnetism is that property occasionally 
possessed by some materials (more especially 
iron and steel) whereby they naturally attract 
or repel one another according to determinate 
laws. 

Lodestone is a peculiar iron ore which 
possesses the property of magnetism. A piece 
of lodestone is a natural magnet. 

Poles 

The poles of a magnet are the portions from 
which the lines of force seem to radiate. A 
magnet has at least one north and one south 
pole, and may have more than two, but there 
will always be an equal number of north and 
south poles. 

The north pole of a magnet is the pole that 
points in the direction of the north pole of the 
earth, and the south pole is the pole of the 
magnet that points to the south when the mag¬ 
net is suspended so that it is free to turn. 


Magnetic Substances 

The common magnetic substances are iron 
and steel, although nickel and cobalt are mag¬ 
netic to a slight extent. 

Bismuth is diamagnetic; that is, it is repelled 
by either pole of a magnet. 

Non-Magnetic Substamces 

Non-magnetic substances are substances 
which are not capable of being magnetized. 
Some of the common metals which are non¬ 
magnetic are: Copper, brass, bronze, alum¬ 
inum, gold, silver, lead, tin, zinc, etc. Such 
materials as wood, glass, paper, rubber, porce¬ 
lain, etc., are also non-magnetic. 

Magnetism will pass through all known sub¬ 
stances; that is, it cannot be insulated. 

Law of Attraction and Repulsion 

Like poles repel one another. Unlike poles 
attract one another. Either pole of a magnet 
attracts magnetic materials which are not mag¬ 
netized with equal force. Magnetic attraction 




272 


ELEMENTS OF ELECTRICITY 


ia inversely proportional to the square of the 
distance (D^) which separates the magnet 
from the material attracted. 

Residual Magnetism 

Residual magnetism is the magnetism re¬ 
tained by a substance after the magnetizing 
force is withdrawn. 

ELECTRICITY 

Three common ways of generating electrical 
charges are: By friction, chemical action and 
induction. 

Conductors 

A conductor is any material that will conduct 
an electric current. 

Insulators 

Any material that offers extremely high re¬ 
sistance to the flow of current is called an in¬ 
sulator. Examples: Porcelain, glass, rubber, 
mica, bakelite, silk, varnish, oil, paraffin, etc. 

Positive and Negative Charges 

Positive and negative are relative terms and 
pertain to the difference in electrical pressures. 
The charge of higher pressure is called the 
positive charge and the charge of lower pres¬ 
sure is called the negative charge. 

Electromotive Force (E. M. F.) 

Electromotive force is the force that causes 
electricity to flow through a circuit. It is some¬ 
times referred to as the “push” in the circuit. 
The terms voltage, pressure, electromotive 
force and potential are synonymous. The unit 
of electrical pressure is called the volt. 

Electric Circuit 

A continuous path for an electric current is 
termed an electric circuit. A circuit may be 
made up of a number of parts—conductors of 
various materials and various appliances. 

Ellectric Current 

An electric current is electricity in motion. 
Current strength is the rate or intensity of flow 
and is analogous to the flow of water in a pipe. 
The unit of current strength or rate of flow is 
the ampere. A current will ’flow only when 
there is a complete circuit and a difference in 
electrical pressure at two points in the circuit. 

Resistance 

Resistance is the opposition offered by a ma¬ 
terial to the flow of electricity through it. 

Electrical Units 

Volt—Unit of electrical pressure. 

Ampere—Unit of current strength. 


Ohm—Unit of resistance. 

Watt—Unit of power. 

Kilowatt—One thousand watts. 

Watt Hour—One watt acting for one hour. 

Kilowatt Hour—One thousand watt hours. 

Ampere Hour—One ampere flowing for one 
hour. 

Farad—Unit of capacity. 

Micro-farad—One-millionth of a farad. 

Ohm’s Law 

The current which flows in a circuit is di¬ 
rectly proportional to the electrical pressure 
(E. M. F.) and inversely proportional to the 
resistance. 

The formulas for the relationship of pres¬ 
sure, current and resistance in an electric cir¬ 
cuit are as follows: 

I = f R = | K = IR. 

Voltage divided by resistance equals current. 

Voltage divided by current equals resistance. 

Current multiplied by resistance equals volt¬ 
age. 

Series Circuit 

Appliances or conductors so connected that 
they form one continuous path are connected 
in series. The resistance of a series circuit is 
equal to the sum of the separate resistances 
which make up the circuit. 

The current in one part of a series circuit is 
equal to the current in any other part of it. 

The pressure which acts upon any part of a 
series circuit is directly proportional to the re¬ 
sistance of that part of the circuit. That is, the 
pressure which acts upon any part of a series 
circuit is in the same proportion to the total 
pressure acting, that the resistance of that part 
of the circuit is to the total resistance of the 
circuit. 

Parallel Circuit 

When two or more circuits are so connected 
that they form separate paths for the current 
to take, they are said to be in parallel. Any one 
of the several paths in parallel may be called 
a “shunt” of the others. The same voltage that 
acts upon one of several circuits in parallel acts 
upon each of the others. 

The current in any one of several circuits in 
parallel is equal to the pressure acting upon the 
circuits divided by its resistance. The total 
current strength in the circuit is equal to the 
sum of the current strengths in the parallel 
paths. 

The joint resistance of parallel circuits is 
equal to the pressure acting upon the circuits 
divided by the total current in them. Also, the 
joint resistance of parallel circuits is equal to 




S U M i\I A R Y 


273 


the reciprocal of the sum of the reciprocals of 
the resistance of the circuits. (The reciprocal 
of a number is equal to one divided by the num¬ 
ber. The reciprocal of a fraction is equal to the 
fraction inverted). 

The joint resistance of parallel circuits which 
have equal resistances is equal to the resistance 
of one of the circuits, divided by the number of 
circuits. That is, 

Joint Resistance = 

R equals the resistance of one circuit. 

N equals the number of circuits. 

Voltage Drop 

Voltage drop is the loss in pressure due 
to overcoming the resistance of a conductor. 
The amount of voltage lost in a circuit is equal 
to the current flowing through it multiplied by 
the resistance of the circuit; that is, E = IR. 

Power 

Electrical power is measured in watts. A 
watt is equal to one ampere flowing under a 
pressure of one volt. The number of watts ex¬ 
pended in a circuit equals the pressure in volts 
acting on the circuit, multiplied by the number 
of amperes of current flowing through it. 
Seven hundred and forty-six watts are equiva¬ 
lent to a mechanical horse-power. 

One kilowatt equals approximately one and 
one-third horse-power. 

Resistance of Conductors 

The resistance of a conductor depends upon: 

(A) The length of the conductor; 

(B) The cross-sectional area (size) of the 
conductor; 

(C) The material of which it is made; 

(D) The temperature of the conductor. 

The resistance of a conductor is directly pro¬ 
portional to its length and inversely propor¬ 
tional to its cross-sectional area (size). 

The resistance changes with a change in 
temperature. For nearly all metals, the resist¬ 
ance increases with an increase in temperature, 
and vice versa. 

The resistance of copper changes .0022 of an 
ohm, for each ohm, with a change of tempera¬ 
ture of one degree. 

The resistance in ohms of a copper con¬ 
ductor may be calculated approximately by the 
following formula: 

Length (in feet) X 10.8 
R =- 

Circular Mils. 

Dry Cells 

The size of a standard dry cell is 2 I/ 2 " x 6". 
The pressure of a dry cell averages 11/2 volts. 


when new. The amount of a current a stand¬ 
ard dry cell will deliver, when short circuited, 
ranges from 15 to 30 amperes, or an average 
of approximately 20 amperes. 

When dry cells are connected in series their 
total pressure is equal to the sum of their sep¬ 
arate pressures. The total resistance of a 
series connection of dry cells is equal to the 
sum of the separate resistances of the cells. 

The current that a series of cells will deliver 
is no greater than the current of a single cell, 
with the exception of the effect of the external 
resistance upon their output. 

A parallel connection of dry cells produces no 
greater pressure than one cell. The ampere 
capacity of cells in parallel is equal to the sum 
of the capacities of the cells in parallel. 

The ability of a parallel connection of cells 
to deliver current depends upon the number of 
cells so connected. 

A combination of the series and parallel con¬ 
nections of cells is called a series-parallel con¬ 
nection. 

A battery is any correct connection of two or 
more cells of any kind. 

STORAGE BATTERY 

A storage battery is an accumulator of 
energy. It does not store electric current, as 
is commonly believed, but accumulates chemi¬ 
cal energy when an electric current is forced 
through it in the proper direction. The chemi¬ 
cal energy stored in a storage battery is ex¬ 
pended as it discharges. 

The voltage of a fully charged storage cell 
averages about 2.2 volts. The voltage of a dis¬ 
charged cell ranges from 1.7 to 1.9 volts. 

The ampere-hour capacity of a storage bat¬ 
tery depends upon the number of the plates 
and the volume and strength of electrolyte. 

An ampere-hour is equal to one ampere of 
current flowing for one hour of time. 

The ampere-hour capacity of a cell is equal 
to the product of the amperes and the hours 
when discharged from fully charged condition 
at a rate of 5 amperes until the voltage of each 
cell falls to 1.8 volts. 

There are usually two charging rates for a 
storage battery, “starting” and “flnishing.” 
The .starting rate is about one-tenth of the 
ampere-hour capacity, and is used until speciflc 
gravity of electrolyte is 1.225 to 1.250, then 
reduced one-half, which is the flnishing rate. 

The speciflc gravity of the electrolyte of 
fully charged storage cells averages 1.285. 
The speciflc gravity of a discharged cell is 
approximately 1.150. 

The speciflc gravity of the electrolyte is 
measured with an instrument called a “hydro¬ 
meter.” 




274 


ELEMENTS OF ELECTRICITY 


The hydrometer reads correctly at 70 degrees 
F. For temperatures other than 70 degrees F., 
corrections must be made, to determine the 
correct specific gravity. For each three de¬ 
grees change of temperature there is one point 
change in the hydrometer reading. For tem¬ 
peratures above 70 degrees F., the corrections 
should be added, and for temperatures below 
70 degrees, the corrections should be sub¬ 
tracted. 

The freezing point of a fully charged battery, 
of the lead plate type, is —90 to —100 de¬ 
grees F. 

The freezing point when discharged is about 
-flO degrees F. 

The battery should not be allowed to stand 
in a discharged condition. Keep the plates and 
separators covered at all times with distilled 
water. Do not add acid or electrolyte to a cell. 

ELECTROMAGNETISM 

When an electric current flows through a 
conductor, a magnetic whirl is set up about it. 
This whirl is in a clockwise direction about the 
conductor, when the current is flowing away 
from the observer and counter-clockwise if the 
current is flowing toward observer. 

A solenoid is a coil of wire without a core. 
A solenoid equipped with a core of magnetic 
material is called an electromagnet. 

The polarity of an electromagnet or sole¬ 
noid depends entirely upon the direction the 
current circulates through the conductor or 
around the core. 

The polarity of an electromagnet can be de¬ 
termined as follows: Grasp the coil in the 
right hand, in such a manner that the fingers 
point in the direction in which the electric cur¬ 
rent flows; the thumb then points to the north 
pole of the electromagnet. 

An ampere-turn is a turn of wire conducting 
one ampere of current. The ampere-turns of a 
coil are equal to the number of turns in the coil, 
multiplied by the number of amperes of current 
flowing in it. The strength of an electro¬ 
magnet depends upon the number of ampere- 
turns and the size, shape and material of the 
core. 

The number of ampere-turns a coil is capable 
of producing depends upon the size of the wire 
and the voltage under which the current is 
forced through it. To wind more or less turns 
of a given size of wire into a coil does not 
change the magnetizing power of the coil, but 
it varies the current because the resistance is 
varied and the current is inversely proportional 
to the resistance of the coil. 

The heating effect is reduced by winding 
more turns into the coil, but its magnetizing 
power remains about constant. A coil of many 


turns is more economical than one of a few 
turns, but is much slower in its action. 

ELECTROMAGNETIC INDUCTION 

When a conductor is moved across a mag¬ 
netic field so that it cuts across the lines of, 
force, an electromotive force is induced in it. 

The strength of the induced E. M. F. depends 
upon the rate at which the lines of force are 
cut. To produce one volt, a conductor must 
cut 100,000,000 lines of force per second. 

An E. M. F. can be induced by moving either 
the conductor or magnetic field, or by moving 
both. The direction in which an induced E. 
M. F. acts depends upon the relative directions 
of the lines of force and the direction the con¬ 
ductor is moving. 

Fleming’s rule to determine the direction that 
an induced E. M. F. acts is as follows: 

Place the thumb, first and second fingers of 
the right hand at right angles to each other. 
Place the hand in such a position that the first 
finger points in .the direction the lines of force 
are fiowing (N. to S.), the thumb pointing the 
direction that the conductor is moved, and the 
middle finger then points in the direction in 
which the induced E. M. F. acts. 

Self-induction in a circuit is the induction 
which results from a variation in current in the 
same circuit. The self-induction in a coil is 
proportional to the square of the number of 
turns. The self-induced E. M. F. in the prim¬ 
ary winding of the average ignition coil some¬ 
times is as high as 200 volts. 

Mutual induction is the induction in one cir¬ 
cuit, caused by a variation of current in an 
adjacent circuit. The operation of an induc¬ 
tion coil depends upon mutual induction. 

BATTERY IGNITION 

The necessary parts of a battery ignition sys¬ 
tem are: An induction coil, usually an ignition 
resistance unit, a breaker or interrupter, a con¬ 
denser, a distributor (if for more than a single 
cylinder engine), spark plugs, a switch, a bat¬ 
tery and the necessary wiring. 

The Ignition Coil 

The ignition coil consists of a soft iron core, 
with primary and secondary windings. The 
primary is a coil of about No. 18 B. & S. copper 
wire (insulated) wound over the core and usu¬ 
ally consists of a few hundred turns. Over the 
primary winding, but well insulated from it, 
is the secondary winding, consisting of many 
thousand turns of very fine copper wire, silk or 
enamel insulated. The battery current fiows 
in the primary. The current induced in the 
secondary fiows through the spark plugs. 



SUMMARY 


275 


The Breaker (Interrupter) 

The breaker is a device that closes and opens 
the primary circuit in time with the engine. 
The spark is produced at the opening of the 
breaker. The breaker is sometimes called a 
timer. 

The Distributor 

The distributor is employed where a single 
coil furnishes the ignition current for more 
than one cylinder. The distributor is really 
a rotating switch. The distributor switches 
the plugs in circuit with the secondary of the 
coil according to the firing order of the en¬ 
gine, hence properly distributes the secondary 
current to the different spark plugs. 

The Condenser 

The condenser has two functions in the igni¬ 
tion system, that of absorbing the self-in¬ 
duced current from the primary winding, thus 
protecting the breaker points from being 
rapidly burned away, and of effecting a more 
nearly complete demagnetization of the core 
of the coil. The three common troubles which 
may develop in connection with the condenser 
are: Shorted condenser, open condenser, and 
loss of capacity. The best way to determine 
when a condenser is functioning properly is to 
observe the arcing at the breaker points and 
the intensity of the spark at the spark plug. 

The Ignition Resistance Unit 

The ignition resistance unit is connected in 
series with the primary circuit. It consists, in 
most cases, of a small coil of iron wire. Its 
resistance is low when cold, but increases 
rapidly as its temperature rises. It protects 
the primary winding from being overheated 
at low engine speed or when the ignition 
switch is closed and the engine not in opera¬ 
tion. If the design of any electrical system 
calls for the use of a resistance unit, it should 
never be operated without one. 

The Polarity Ignition Switch 

The polarity switch as used with the bat¬ 
tery ignition system, is to reverse the primary 
current through the breaker each time the 
switch is closed. It causes the contacts to 
burn more evenly, as the metal that is carried 
from one point to the other during a period of 
operation will be carried back during the next 
period of operation. 

Breaker Point Adjustment 

The breaker points should be dressed with 
a file or oilstone so that they strike squarely 
together. The air gap between the breaker 
points of ignition systems range from .006" to 
.030", with an average of .012" to .020". 


Spark Plugs 

The air gap in spark plugs varies from 
.025" to .030" for average systems. On some 
of the magneto systems it is advised to make 
the gap much smaller to assist in starting. 
Keep the spark plugs clean and have the gaps 
of all the plugs of an engine equal. 

MAGNETOS 

A magneto is a device used to convert me¬ 
chanical energy into electrical energy. The 
magnetic field of a magneto is furnished by 
permanent magnets. The armature of a mag¬ 
neto is the portion of the magneto in which 
the E. M. F. is induced. The armature may be 
of either the revolving or stationary type. Mag¬ 
netos used for ignition purposes are usually 
equipped with a breaker mechanism and dis¬ 
tributor, although the latter is not necessary 
when used on single cylinder engines. 

Types of Magnetos 

Magnetos are divided into three different 
types: 

(A) The revolving armature type. 

(B) The inductor type. 

(C) The revolving field type (Ford). 

Magneto Classifications 

Magnetos are divided into five different 
classes, viz: 

(A) Straight low tension, (“Make and 
break”), (not used on automobiles). 

(B) Low tension dual. 

(C) Straight high tension. 

(D) High tension dual. 

(E) High tension duplex, (single spark 
and vibrating spark). 

The magnetos in the above classifications 
may be of either the revolving armature type 
or inductor type. 

The magnetos in which the induced E. M. F. 
reaches the peak of the wave twice in one 
revolution are driven at the following speeds: 

The armature of the magneto for four cyl¬ 
inder engines is driven at crankshaft speed. 

The armature of the magneto for six cylinder 
engines is driven at one and one half crank¬ 
shaft speed. 

The armature of the magneto for eight 
cylinder engines is driven at twice crankshaft 
speed. 

SPARK ADVANCE 

Most ignition systems are designed in such 
a manner that the time of the spark in relation 
to piston position may be varied so as to occur 
earlier or later. 

To cause the spark to occur earlier in re- 



276 


ELEMENTS OP ELECTRICITY 


lation to the position of the piston, is advanc¬ 
ing the spark. To cause the spark to occur 
later in relation to piston travel, is retarding 
the spark. The necessity of advancing the 
spark is caused by the lapse of time between 
the production of the spark and the occurrence 
of the explosion. The lapse of time is practic¬ 
ally constant, hence at high engine speed the 
spark must be produced before the piston 
reaches top dead center in order to have the 
explosion occur before the piston has moved 
down on the power stroke. 

Automatic Spark Advance 

The spark is automatically advanced on 
some systems by the use of a specially con¬ 
structed mechanism, operating upon the prin¬ 
ciple of the centrifugal governor. As the speed 
of engine increases, the breaker cam is auto¬ 
matically moved ahead of the shaft that 
drives it. 

Where both manual and automatic advance 
is used, the range of advance is equal to the 
sum of the number of degrees obtained by each 
of them when used separately. 


IGNITION TIMING 

Ignition timing is so setting the breaker 
mechanism that the ignition spark will occur, 
each time a piston of the engine moves up to 
the firing point. 

The firing point of the average engine is a 
few degrees past top dead center at the end of 
the compression stroke, with a fully retarded 
spark. There are exceptions to this rule, as 
some engines are timed to fire in full retard 
at top dead center, while still others are timed 
to fire a few degrees before top dead center. 

When timing ignition. No. 1 piston should be 
set at top dead center at the end of the com¬ 
pression stroke. 

The breaker mechanism should be set in full 
retard and the breaker cam turned in its direc¬ 
tion of rotation until the points are just separa¬ 
ting. Lock the cam in this position. Wire 
the distributor terminal to which the distribu¬ 
tor brush points, to No. 1 spark plug. Wire the 
remaining spark plugs to the other distributor 
terminals according to distributor brush rota¬ 
tion and the firing order of the engine. 


i 

s 

i 





ELEMENTS OF ELECTRICITY 


277 


QUESTIONS 


1. What is lodestone? 

2. Define magnetic materials; non-mag- 
netic materials. 

3. What materials are used when mag¬ 
netic properties are necessary? 

4. What are the poles of a magnet? Is one 
pole stronger than the other? 

0 . Can a magnet have two north poles and 
no south pole? 

6. What is the north pole of a magnet? 

7. Name five characteristics of magnetic 
lines of force. 

8. Describe the magnetic compass needle. 
What causes the compass needle to point 
north? 

9. What is the theoretical difference be¬ 
tween a magnetized bar of iron or steel and an 
unmagnetized bar? 

10. Define each of the following terms: 
(a) permeability, (b) retentivity, (c) reluct¬ 
ance, (d) residual magnetism. 

11. What is a keeper? How can magnets 
be assembled so one magnet is a keeper for the 
other? 

12. How should a compound magnet be as¬ 
sembled? If unlike poles are placed together 
what is the result? 

13. Give three ways of producing an elec¬ 
tric charge. 

14. Define conductor; insulator. 

15. Explain what is meant by the terms 
“positive charge” and “negative charge.” 

16. Define E. M. F. 

17. What is meant by the term, “electric 
circuit.” 

18. What is an electric current? What is 
necessary to produce an electric current? 

19. Upon what does the strength of an elec¬ 
tric current depend? 

20. Define volt, ampere and ohm. 

21. What is Ohm’s Law? 

22. Describe a series connection of electri¬ 
cal appliances. 

23. What is voltage drop? 

24. Describe a parallel connection of appli¬ 
ances. To what is the joint resistance of ap¬ 
pliances in parallel equal? 

25. What is a watt? 

26. Define the term “resistance.” 

27. Upon what does the resistance of a con¬ 
ductor depend? 

28. What is a circular mil foot? 

29. What are the parts of a simple cell? 

30. When is a cell said to be discharged? 


31. What is the voltage of a standard dry 
cell? The short-circuit ampere capacity? 

32. What is an electric battery? 

33. For what reason are cells connected in 
series? What is the total ampere capacity of 
cells in series? 

34. For what reason are cells connected in 
parallel? What is the total voltage of cells in 
parallel? 

35. How is the total voltage of cells in ser¬ 
ies-parallel found? The total ampere capacity? 

36. Does a storage battery store electricity? 

37. Of what are the positive plates of a stor¬ 
age battery made? Of what are the negative 
plates made? 

38. Define the term “electrolyte.” 

39. What are separators? What is their 
purpose in a storage cell? 

40. What is a positive group? A negative 
group? 

41. Define element. 

42. Define specific gravity. 

43. What is a hydrometer? In connection 
with storage batteries what use is made of a 
hydrometer? 

44. When the temperature of electrolyte is 
above 70 F., is the temperature correction for 
the hydrometer added or subtracted? 

45. How is the ampere-hour capacity of a 
storage battery determined? 

46. Upon what does the voltage of a storage 
battery depend? The ampere-hour capacity? 

47. Is anything taken from a storage cell 
when it discharges? 

48. What causes storage cells to gas when 
charging? 

49. Why is it necessary to add water to 
storage cells? 

50. What is meant by the term corroded 
battery terminals? What should be done when 
the terminals become corroded? 

51. Why should a battery be charged for a 
while after water has been added, before meas¬ 
uring the specific gravity of the electrolyte? 

52. In winter why should a storage battery 
be charged for a period after the water has 
been added to the cells? 

53. Draw a diagram to show how a storage 
battery may be charged from a 110 volt D. C. 
lighting circuit. Use a bank of lamps for a 
charging resistance. 

54. Upon what does the strength of the 
magnetic field set up about an electric con¬ 
ductor depend? 

55. Upon what does the direction of the 





278 


ELEMENTS OF ELECTRICITY 


flow of the lines of force about the current de¬ 
pend ? 

56. What is a solenoid? 

57. Upon what does the strength of the 
magnetic field set up by current in a solenoid 
depend? 

58. Upon what do the ampere-turns of a 
coil depend? 

59. How is an electromagnet made? 

60. Upon what does the polarity of an elec¬ 
tromagnet depend? 

61. Upon what does the strength of an elec¬ 
tromagnet depend? 

62. When a conductor is moved across a 
magnetic field, upon what does the induced 
E. M. F. depend? 

63. Upon what does the direction of the in¬ 
duced E. M. F. depend? 

64. What is self-induction? How does self- 
induction affect a circuit? 

65. Upon what does the self-induction of a 
circuit depend? 

66. What is mutual induction? 

67. What is an induction coil? 

68. What are the necessary parts of an in¬ 
duction coil? 

69. Why is the core of an induction coil 
made of soft iron wires instead of solid steel? 

70. Upon what three things does the 
strength of the induced E. M. F. in secondary 
depend? 

71. Which winding, primary or secondary, 
is first wound over the core? 

72. Which winding has the most turns? 

73. Is a connection between the primary 
and the secondary necessary? 

74. Does the battery current flow through 
the secondary? 

75. When the circuit through the primary 
of the coil is closed, is there an E. M. F. in¬ 
duced in the primary winding? In the second¬ 
ary? 

76. Is there an E. M. F. induced in the 
primary when the primary circuit is broken? 

77. What is the purpose of a condenser in 
the ignition system? 

78. Upon what three things does the capac¬ 
ity of a condenser depend? 

79. In what relation to the breaker is the 
condenser connected? 

80. How is a condenser made? 

81. What is shorted condenser? Open con¬ 
denser? Punctured condenser? 

82. Explain how a condenser can be tested. 

83. Does the condenser discharge through 
the breaker points when they close, through 
the primary or through the secondary? 

84. How can the secondary winding of the 
coil be tested? 

85. What is an ignition resistance unit? 
What is its purpose? 


86. Explain the difference between open 
circuit type breakers and closed circuit type 
breakers. 

87. What is a distributor? 

88. What is a polarity ignition switch? 

89. Why is it necessary to advance and re¬ 
tard the spark? 

90. What is an automatic spark advance 

and retard? Under what conditions is a man¬ 
ual control of the spark better than the auto¬ 
matic control? , . . ^ 

91. Define the terms “breaker” and ‘inter¬ 
rupter.” 

92. What is the difference in construction 
between primary cable and secondary cable? 

93. What is the purpose of the induction 
coil in the ignition system? 

94. What is a spark plug? What is the 
difference between an inseparable plug and the 
separable plugs? 

95. What is the difference between the taper 
threaded plug and the plug having the S. A. E. 
standard base? 

96. What is a magneto? 

97. Why is the base of a magneto made of 
bronze or aluminum? 

98. What is the armature of a magneto? 

99. When the breaker points are in full ad¬ 
vance what should the approximate position of 
the distributor brush be? 

100. What is clockwise magneto? Counter 
clockwise or anti-clockwise magneto? 

101. How can a clockwise magneto be dis¬ 
tinguished from a counter clockwise magneto? 

102. What is used to recharge magnets? 

103. What must one be careful about when 
recharging magnets? 

104. How should magnets be placed on a 
magneto? 

105. Does a magneto produce alternating 
or direct current? 

106. Explain what is meant by internal 
timing? 

107. Explain how to check up the internal 
timing of a magneto. 

108. Is an induction coil necessary with a 
low tension magneto? 

109. Describe the low tension dual magneto 
ignition system. 

110. Describe the high tension magneto. 
How does it differ from the low tension mag¬ 
neto? How can one be distinguished from the 
other? 

111. How many windings are there on the 
armature core of a high tension magneto? 

112. Are the primary and secondary wind¬ 
ings connected together? 

113. One end of the primary winding of a 
straight high tension magneto is grounded; to 
what is the other connected? 

114. Where is the condenser located and to 





ELEMENTARY ELECTRICITY 


279 


what is each of its terminals connected when 
used with the high tension magneto? 

115. For what is the pencil used? 

116. What is the collector brush? 

117. How is the ignition cut off when using 
a high tension magneto? 

118. What is the purpose of a safety gap? 

119. Explain how the condenser of a high 
tension revolving armature type magneto can 
be tested. 

120. Do all magnetos have pencils? 

121. How can the engine be started if the 
pencil from the magneto had been lost? 

122. What is the position of the armature 
core with relation to the pole pieces when the 
breaker points separate in full advance? 

123. With the breaker points separated, 
should test buzzer sound when one test point 
is on one breaker point and the other test 
point on the other breaker point? 

124. Why is it easier to start an engine with 
battery ignition than with a high tension mag¬ 
neto ? 

125. State the difference between the high 
tension dual magneto and the straight high 
tension magneto. 

126. Do all high tension dual magnetos 
have a condenser in the magneto? 

127. What causes sparking at the safety 
gap of a magneto? 

128. In what way does a high tension duplex 
magneto differ from the high tension dual mag¬ 
neto? 

129. How does the inductor type magneto 
differ from the revolving armature type? 


130. How can an inductor type magneto be 
distinguished from a revolving armature type? 

131. When the distributor brush of a six 
cylinder revolving armature type magneto has 
made one revolution, how many has the arma¬ 
ture made? 

132. Why cannot steel screws be used to 
secure the poles of the magnets to the flywheel 
on Ford magneto? 

133. How are the coils of armature of a 
Ford magneto connected? If one volt is gener¬ 
ated in each coil, how many volts in the entire 
armature? 

134. What should the air gap between the 
pole pieces of the magnets be? How is their 
gap adjusted? 

135. Explain how to test the armature for— 
(a) open coils, (b) shorted coils, (c) grounded 
coils. 

136. Why are four induction coils neces¬ 
sary in the Ford ignition system? 

137. How many adjustments on the Ford 
vibrator and how made? 

138. What is the purpose of the vibrators? 

139. What is the purpose of the timer? 

140. How is the spark advanced and re¬ 
tarded? 

141. Describe fully how to time the igni¬ 
tion of a four cylinder engine when a magneto 
is used. 

142. Describe fully how to time the igni¬ 
tion of an engine having a battery ignition sys¬ 
tem. 



GENERATORS AND MOTORS 


A dynamo is a machine for converting me¬ 
chanical energy into electrical energy, or elec¬ 
trical energy into mechanical energy. The 
dynamo, when used to transform mechanical 
energy into electrical energy, is called a gen¬ 
erator; and when used to transform electrical 
energy into mechanical energy is called a 
motor. The dynamo consists fundamentally 
of two parts; namely, field—the frame, field 
poles, and field coils which form an electro¬ 
magnet—and the armature which revolves 
between the field poles. 


toward the observer. Since the E. M. F. in¬ 
duced in one side is in the opposite direction 
to that in the other side, they act jointly to 
produce a fiow of electricity around the loop 
as indicated by the arrows. There is no in¬ 
duced E. M. F. in the ends of the loop, since 
they cut no lines of force. 

The strength of the induced E. M. F. in 
either side of the loop at any instant, depends 
upon the number of magnetic lines of force cut 
by the conductor per second. The number of 
lines cut depends upon the length of the side 


\ 



The Simple Alternator. (Single Loop Armature) 

If a single loop of wire is revolved in the 
magnetic field, as shown in Fig. 274, an E. M. 
F. will be induced in the sides of the loop. 
If the ends of the loop are connected to metal 
rings (F) and (G) upon which the brushes 
(H) and (I) ride, the induced E. M. F. will pro¬ 
duce current in a circuit such as is formed 
when a lamp (K) is connected to the brushes. 
The direction of the induced E. M. F. in the 
sides of the loop may be determined by Flem¬ 
ing’s Right Hand Rule. 

The motion of one side of the loop with 
respect to the magnetic field is just the reverse 
of the motion of the other side. As a result of 
this difference in motion the E. M. F. induced 
in the side (AB) is from the observer, while 
the E. M. F. induced in the other side (CD) is 


in the magnetic field, the strength of the mag¬ 
netic field, and the number of revolutions per 
second. If the strength of the magnetic field 
is uniform—that is, the same in every part of 
the field—and remains constant in value and 
the loop revolves about its axis at constant 
speed, the induced E. M. F. in either side of 
the loop will change in value, due only to a 
change in direction of motion of the two sides 
with respect to the magnetic field. When the 
loop is in a horizontal position, as shown, the 
direction of the field also being horizontal, the 
two sides of the loop are moving in a path, 
for an instant, perpendicular to the direction 
of the magnetic field, and the rapidity with 
which the sides cut the lines of force is great¬ 
est, hence the induced E. M. F. of the loop is 
at a maximum. 

















GENERATORS AND MOTORS 


281 


The value of the induced E. M. F. for any 
other positions of the loop depends upon the 
angle at which the sides are moving with re¬ 
lation to the direction of the magnetic field. 
When the loop reaches a vertical position, the 
sides, for an instant, are moving parallel to 
the lines of force and so there is no E. M. F. 
induced in the loop. The direction of the in¬ 
duced E. M. F. reverses as the sides of the loop 
change places each half revolution, hence the 
current which flows in the circuit is an alter¬ 
nating current. 

Simple Direct Current Generator 

The E. M. F. induced in the loop of wire de- 


a direct current generator, because it forces 
electricity through the external circuit in one 
direction only. The two segment rings con¬ 
stitute a simple commutator, and its pur¬ 
pose, as pointed out, is to reverse the con¬ 
nection of the loop with respect to the ex¬ 
ternal circuit as the induced E. M. F. in the 
loop changes. A single loop machine as just 
described can not be put to any satisfactory 
use and is of importance only in showing the 
principles of a generator. 

Ring Wound Armature 

A better form of armature winding for direct 
current dynamos is shown in Fig. 276. This 



scribed in the previous section may be made to 
produce a direct current-—one that flows in one 
direction—in the external circuit in following 
way: Replace the two continuous metallic 
rings with a single ring composed of two 
segments that are insulated from each other. 
(See Fig. 275.) If now the two brushes, 
which are insulated from each other, are 
so mounted that they rest upon the insula¬ 
tion between the segments when the induced 
E. M. F. in the loop is zero, the connection of 
the external circuit with respect to the loop 
will be reversed at the same instant the direc¬ 
tion of the induced E. M. F. in the loop changes 
and then the induced E. M. F. in the loop 
always acts to send a current through the ex¬ 
ternal circuit in one direction. 

Such a machine as just described constitutes 


armature is called a ring wound armature since 
the coils which revolve in the magnetic field 
are wound around an iron ring. The iron ring 
supports the coils, and forms a path of low 
reluctance for the lines of force from one pole 
to the other. Because of the low reluctance 
offered to the flow of the lines of force by the 
iron ring, it is possible to set up many more 
lines in the space in which the coils revolve than 
would be possible were the ring not provided. 
The path of the magnetic lines of force is out 
of the north pole through the air gap between 
the pole and the ring, into the ring, around the 
ring in both directions to the opposite side, 
through the air gap between the side of the 
ring and the south pole, into the south pole, 
and through the frame back to the north pole. 






















282 


ADVANCED ELECTRICITY 


With the poles magnetized, a magnetic field is 
set up on both sides of the ring in the spaces 
between it and the poles. There is no field set 
up inside of the ring, since the lines of force 
follow around the ring from one side to the 
other as shown by the dotted lines in the 
illustration. 

There are as many commutator segments as 
there are coils on the ring. One end of each 
coil connects to one commutator segment and 
the other end to an adjacent segment. All of 
the commutator segments are connected to¬ 
gether through the armature coils, but as they 
are assembled to make up the commutator, 
each is carefully insulated from the other. 


ture are equal and in opposite directions there 
i.s no fiow of electricity through the armature 
until a connection is made from the top of the 
commutator through an external circuit to the 
bottom of the commutator. 

Connection to the commutator is made by 
means of soft carbon blocks called brushes. 
These brushes are held in such position with 
relation to the poles that, when a coil is mov¬ 
ing parallel to the lines of force, the brush rests 
on the commutator segments to which the 
coil connects. There are always some of the 
armature coils cutting magnetic lines of force 
as long as the ring is revolved in the field be¬ 
tween the poles, and the connection between 



The action of the ring-wound armature can 
be studied from Fig. 276. As the armature is 
revolved, the outsides of the armature coils cut 
the lines of force, hence E. M. F. is induced in 
them. Determine the direction of the induced 
E. M. F. by Fleming’s Right Hand Rule. 
As indicated by arrowheads and as deter¬ 
mined by the right hand rule, the induced 
E. M. F. in one side of the armature tends 
to pull the electricity through the armature in 
the opposite direction to that in the other side. 
Since the E. M. F’s. in either side of the arma- 


these coils and the external circuit as made 
through the brushes and commutator seg¬ 
ments is switched in such manner that the 
induced E. M. F. forces electricity through the 
external circuit in one direction. 

Since there are always armature coils cut¬ 
ting the lines of force there is an unbroken 
E. M. F. in the armature to keep the current 
fiowing through the external circuit. As one 
coil turns out of the magnetic field into a 
neutral point (the point where the coil moves 
parallel to the lines of force) another coil turns 

































GENERATORS AND MOTORS 


283 


out of the neutral point and into the magnetic 
field. 

An armature of this type may have almost 
any number of armature coils so long as there 
are an equal number of commutator segments 
and the ends of the coil are connected to ad¬ 
jacent segments. The more coils and seg¬ 
ments the armature has, the more nearly con¬ 
stant will be the generated E. M. F. If there 
are only a few coils, a varying E. M. F. is gen- 


figures showing the ring wound armature are 
better for illustrating the principles of gen¬ 
erators and motors than the drum winding, 
as the circuits through the armature are more 
easily traced. The drum winding has a decided 
advantage over the ring winding, since the 
armature can be made more compact, and is 
more efficient, because both sides of the coils 
cut the lines of force. 

In the drum winding the coils are wound 





FIG. 277 


erated, which causes the current to pulsate 
through the circuit. 

Drum Wound Armature 

The ring wound armature is now out of date 
and is practically no longer used. However, 


around a core so that both sides of each 
coil are in slots in the armature. If the arma¬ 
ture is wound for a two-pole machine, the 
sides of each coil are wound in slots about 
180° apart, and the ends of the coils con¬ 
nect to adjacent commutator segments. 










































284 


ADVANCED ELECTRICITY 


Fig. 277 shows a drum winding for a two- 
pole armature having nine armature slots, and 
nine segments in the commutator. The arma¬ 
ture is shown cone shaped to make it possible 
to trace the circuits through the winding from 
the figure. In practice a cone-shaped arma¬ 
ture is seldom used but instead the armature 
is cylindrical in shape. To make the circuits 
clear, the figure shows each coil as consisting 
of one turn, but the coils in armatures for 
motors and generators usually consist of many 
turns per coil. 

The coils for a two-pole armature are wound 
with their sides about 180° apart in order that 
the E. M. P. induced in one side may act in 
the opposite direction to that induced in the 
other. If the E. M. F. acts in the same direc- 


coils are connected to adjacent commutator 
segments. Fig. 278, right, shows a star pro¬ 
jection of a lap winding for a four-pole arma¬ 
ture having nine armature slots and nine com¬ 
mutator segments. As many brushes as there 
are poles in the machine are necessary to com¬ 
plete the armature circuits. Pig. 279, top 
center, shows the field arrangement for a four- 
pole machine. There are four neutral points 
in a four-pole machine instead of two as in a 
two-pole machine. The brushes are so placed 
on the commutator that they rest on commu¬ 
tator segments connected to coils which lie in 
neutral points. The brushes are spaced 90° 
apart, and the brushes diametrically opposite 
being at equal electrical pressure are connected 
to same terminals. 



WAVE WOUND FOUR POLE ARMATURE 


LAP WOUND FOUR POLE ARMATURE 


FIG. 278 


tion in both sides of the coil, the E. M. P. in 
one side acts against that in the other and 
no current will fiow. 

Very few armatures have an even number 
of armature slots, hence, the coils are not 
wound so that the sides are exactly 180° apart. 
This construction causes one side of each 
armature coil to pass through the neutral 
point a little before the other side, resulting 
in better commutation, and thereby reducing 
sparking at the brushes to a minimum. 

Four Pole Armature 

The armature coils of a four-pole armature 
are wound in armature slots in such manner 
that the sides of each coil are about 90° apart. 
If the lap winding is used, the ends of the 


If the wave winding is used, the sides of each 
of the coils are wound in slots about 90 de¬ 
grees apart the same as in the lap winding, 
but the ends of the armature coils connect to 
commutator segments about 180° apart. 
Pig. 278, at the left, shows a star projection of 
a wave winding for a four-pole armature hav¬ 
ing nine slots and nine commutator segments. 
Only two brushes are necessary to complete 
the circuits through the armature; however, 
four brushes may be used as with the lap wind¬ 
ing. Where only two brushes are used they are 
placed 90° apart and in such position with 
relation to the field poles that they are on com¬ 
mutator segments connected to coils that lie 
in the neutral points. When four brushes are 
used, the brushes, as with the lap winding, are 



























GENERATORS AND MOTORS 


285 


set 90° apart, and the brushes diametrically 
opposite being at the same electrical pressure 
are connected to the same terminal. 

Magnetic Circuits and Field Windings for 
Generators and Motors 

In the previous discussion of the generation 
of an E. M. P. in the armature of a generator 
by revolving it in a magnetic field, the field was 
assumed and nothing was said as to how 
it is set up. The field may be set up by 
permanent magnets, or by electromagnets. 
Permanent magnets are not strong enough to 
set up a field suitable for any but very small 
machines. Permanent magnets are used for 
magnetos. Electromagnets are used for motors 
and generators. 


two field coils. Illustration, lower left, shows a 
magnetic circuit of a two pole machine using 
one field coil. Illustration, lower right, shows 
another arrangement of a two pole field frame 
arranged for a single field coil. 

The magnetic circuit of almost any dynamo 
is composed of the following parts: The arma¬ 
ture core, which is usually a cylinder of lam¬ 
inated iron mounted on a shaft and having 
slots cut in its surface to carry the armature 
coils; the air gap, which is the clearance be¬ 
tween the armature and the ends of the poles; 
the pole shoes, or pole pieces, which are some¬ 
times cast integral with the frame, and some¬ 
times fastened into the frame with screws or 
bolts; and the frame, or yoke, which carries the 
pole pieces, and at the same time serves as a 





FIG. 279 



The term “field” applies specifically to the 
magnetic lines of force set up between the 
poles of the field magnets, and in general to the 
entire magnetic circuit of a machine. Various 
forms of “fields” (magnetic circuits) are 
shown in Fig. 279. The upper left illustration 
shows the magnetic circuit of a two pole round 
frame type machine. Illustration top center 
shows the magnetic circuit of a four pole round 
frame type machine. In each of these two ma¬ 
chines, field coils are placed on each of the 
poles. Illustration, upper right, shows a mag¬ 
netic circuit of a two pole machine using two 
field coils. Illustration, lower centre, shows a 
magnetic circuit for a four pole machine using 


support for the other parts of the machine. 

There are two kinds of field coils—series 
and shunt. The series field coils are of com¬ 
paratively few turns of heavy wire, some¬ 
times copper ribbon, and are connected in series 
with the armature. The resistance of series 
field coils is very low. Shunt field coils are 
many turns of comparatively small wire and 
are connected in parallel with the armature. 
The resistance of shunt field coils is usually 
several ohms. Fig. 283 shows a machine with 
series field coils. The arrows show the di¬ 
rection of fiow of current through the field 
coils and the armature when the machine 
is run as a motor. Machines having only 




















































286 


ADVANCED ELECTRICITY 


series field coils are called series wound ma¬ 
chines. Series wound generators are not used 
on the automobile, but series wound motors 
are used. 

Figs. 276 and 280 show machines with shunt 
field coils. The arrows indicate the direction 
of flow of current when the machine is run as 
a generator. When the machine is run as a 
generator there must be some residual mag¬ 
netism for it to “build up” from, and the field 
coils must be so wound and connected that as 
the generator builds up it forces current 
through them in the direction to magnetize the 
poles to a greater strength. If the field coils 
are not properly connected, the generator will 
not build up from its residual magnetism, since 


is called a differential compound machine. 
Starting motors seldom have the shunt field 
winding, but when compounded they are al¬ 
ways cumulative. Generators used on the 
automobile are usually straight shunt wound. 
The generators which are compounded are 
usually differentially wound. If the field coils 
are connected so that a machine will run as a 
compound cumulative motor, it will operate as 
a compound differentially wound generator. 

The straight shunt wound generator gives 
about constant voltage when driven at con¬ 
stant speed. However, if the load is increased 
on a straight shunt generator which is driven 
at constant speed, the voltage will drop slightly 
because of field distortion and IR-drop. If the 



it tends to force current through them in the 
direction to demagnetize rather than mag¬ 
netize the poles. 

Machines having both shunt and series field 
coils are called compound machines. When 
the series and the shunt field coils are so wound 
and connected that current in both magnetizes 
the pole pieces to a greater strength, it is 
called a cumulative compound machine. If 
the field coils are so wound and connected 
that the current in the shunt field coil mag¬ 
netizes the poles and the current in the series 
field coils tends to demagnetize the poles, it 


machine is driven at variable speeds its voltage 
varies almost with the square of the speed. 
That is, doubling the speed causes the ma¬ 
chine to generate about four times the voltage 
—tripling the speed causes the machine to gen¬ 
erate almost nine times the voltage, etc. A 
compound differential wound generator builds 
up to a voltage that will cause the cur¬ 
rent to flow through the external circuit at a 
certain strength but will not build up much 
beyond this value, even though the speed of 
the machine is further increased. 











































GENERATORS AND MOTORS 


2S7 


Field Distortion 

As the current passes through the arma¬ 
ture of a generator, magnetic lines of force are 
set up about the armature conductors. The 
lines about the armature conductors crowd the 
lines forming the field forward and so twist the 
field out of its natural path. This twisting of 
the field is called “field distortion.” The degree 
to which a field is distorted depends on the 
strength of the current in the armature and the 
strength of the field. The stronger the field 


at right angles to the lines of force, a force 
is set up which moves or tends to move the 
conductor across the field. The cause of this 
force is shown in Fig. 284. When the current 
is passed through the conductor, magnetic lines 
of force are set up about it which crowd the 
lines forming the field to one side of the con¬ 
ductor. As the lines of force are crowded to 
one side of the conductor they are pushed out 
of their natural path, and as they tend to 
straighten out they exert a force which acts to 
move the conductor across the field. The 



DASH LIGHT 

TO TAIL LIGHT 
TO HEAD LIGHTS 


SWITCH 

CURRENT 

INDICATOR 


GROUND TO FRAME 


FIG. 281 


ESSEX STARTING, LIGHTING AND IGNITION SYSTEM—DELCO 


the less it is distorted by the armature current 
and the stronger the armature current the 
more the field is distorted. 

Field distortion causes the neutral points to 
shift and so causes the points of commutation 
to move forward as the load of the generator 
increases. For this reason the brushes of a 
generator must be set a little ahead to be on 
the points of the commutation while the load 
is on. (See Fig. 280.) 

PRINCIPLES OF ELECTRIC MOTOR 

When an electric current is passed through 
a conductor which is lying in a magnetic field 


strength of the force depends upon the 
strength of the field and the strength of the 
current. The direction a conductor is moved, 
depends upon the direction of the field and the 
direction of current. 

The relation which exists between the direc¬ 
tion of the field, the direction of the current, and 
the direction the conductor is moved, can well 
be remembered by an application of the Left- 
Hand or Motor Rule. Rule: Place the thumb, 
first finger, and middle finger of left hand at 
right angles to each other. Then place the 
hand so the first finger points in the direction 
of the magnetic field, the middle finger in the 



































288 


ADVANCED ELECTRICITY 


direction the current flows, and the thumb will 
point in the direction the conductor is moved. 

Action of Electric Motor 

The essential parts of a direct current motor 
are identical with those of a direct current 
generator—they are an armature and a mag¬ 
netic fleld. A direct current motor can be 
run as a direct current generator, or a direct 
current generator can be run as a direct cur¬ 
rent motor. 

The brushes, as in the generator, are placed 
on the commutator in such position with re¬ 
lation to the fleld poles that they rest on seg¬ 
ments to which the coils in the neutral points 
connect. As the armature turns, the brushes 




riding on the commutator segments keep the 
armature coils switched into the circuit, so 
that the current in the coils beneath the south 
pole flows in the opposite direction to the cur¬ 
rent in the coils beneath the north pole. 

Fig. 283 shows a series wound machine with 
a ring wound armature. When the switch (S) 
is closed the E. M. F. of the battery causes cur¬ 
rent to flow through the fleld coils (F) and 
through the armature. The current flowing 
through the fleld coils magnetizes the poles 
and so sets up the fleld. The current in the 
conductors as they pass positions (A), (B), 
(C), (D) and (E) flows in, or away from ob¬ 
server, and as they pass positions (I), (J), (K), 
(L) and (M) it flows out or towards the ob¬ 
server. The conductors as they pass positions 


(H) and (G) are in the neutral points, hence 
are not in circuit with battery. By applying the 
left hand or motor rule, the direction the arma¬ 
ture conductors are moved can easily be deter¬ 
mined. Those beneath the north pole are moved 
up and those beneath the south pole are moved 
down. This produces a twisting force on the 
armature that turns it clockwise. The action 
of the commutator and the brushes keeps the 
coils switched into the circuit so there is a 
constant twisting force maintained in the 
armature. The strength of this twisting force 
depends upon the strength of the fleld, the 
strength of the current in the armature and 
the manner in which the armature is wound. 

The direction a motor runs depends upon 
the direction of the current through the arma¬ 



ture and the direction of the magnetic fleld. 
If the connections to the battery are re¬ 
versed, the direction of the current through the 
armature will be reversed and the polarity 
of the fleld reversed. Since the current in 
both the armature and the fleld is reversed 
the motor runs the same direction. This 
should be verifled by the left-hand rule. If the 
polarity of the fleld is reversed without revers¬ 
ing the current through the armature, the 
motor runs in the opposite direction. Or, if 
the direction of the current through the arma¬ 
ture is reversed without reversing the polarity 
of the fleld, the motor runs in the opposite 
direction. Verify these statements by the left 
hand rule. 

The action of the drum wound armature is 





























GENERATORS AND MOTORS 


289 


about the same as a ring wound armature, 
since it is so wound that the current through 
the conductors beneath the south pole will be 
in the opposite direction to the current in the 
conductors beneath the north pole. The drum 
windings for a motor armature are fundamen¬ 
tally the same as those for the generator. 

Armature Reaction in Motor, 

Field Distortion 

When current flows in the armature wind¬ 
ing of a motor, a magnetizing effect is pro¬ 
duced on the armature core, which twists 


Points of Commutation 

The points of commutation are the points on 
a commutator where the brushes should be 
placed. The points of commutation are de¬ 
termined by the neutral points. The brushes 
should be so placed on the commutator that 
they rest a little back of commutator seg¬ 
ments which connect to coils that are in the 
neutral points. The true points of commuta¬ 
tion can only be found by adjusting the brushes 
while the motor is running. If the brushes are 
not on the points of commutation the motor 


mm 



msm 


+ 


r 

Jt 

© ( 

) 

1 ©^ 



© 1 






FIG. 283 


the fleld out of its direct path through the 
armature core from pole to pole. This twist¬ 
ing of the fleld out of its natural path is called 
fleld distortion. Distortion of the fleld causes 
the neutral points to shift, and in turn, the 
points where the brushes must rest will move. 
In the motor the field is distorted in the 
direction opposite to which the armature turns. 
(See Fig. 284.) Therefore the neutral points, 
when the motor is running, are back of the 
position they would be in if the field was not 
distorted by the armature current. The dis¬ 
tance the neutral points move depends upon 
the degree of field distortion and the distortion 
depends upon the strength of the field and the 
strength of the armature current. 


Will not develop full power, and there will be 
sparking at the brushes. 

To find the points of commutation the brush 
rigging is loosened, and with motor under load, 
the brushes moved forward or backward till 
the sparking is reduced to a minimum and the 
motor develops maximum power. Then lock 
brush rigging in that positi 9 n. The brush 
rigging of some motors is so set at the factory 
that it cannot be moved, hence is not adjust¬ 
able. In this case, the points of commutation 
are determined at the factory and then the 
brush holder fastened securely to the end plate 
of motor. The brush rigging of other motors is 
slotted and so is adjustable. If the brush rigg¬ 
ing is to be removed it should be marked so that 








































290 


ADVANCED ELECTRICITY 


it can* be replaced with less difficulty. If, for 
some reason, the brush rigging becomes so 
loose that the brushes have moved off of the 
points of commutation, the commutator is 
likely to be badly burned. 

Counter Electromotive Force 

When the armature of a motor revolves in 
the magnetic field, an E. M. F. is generated in 
the coils, much the same as the E. M. F. gen¬ 
erated in the armature coils of a generator. 
This E. M. F. is induced in the sides of the coil 
as they cut the lines of force while the arma¬ 
ture revolves. The direction of this E. M. F. is 
counter, or against, the flow of current through 
the armature, and so is called counter E. M. F. 
The counter E. M. F. of a motor depends upon 


Speed of Motor 

The speed of a motor is always such that the 
torque produced is just ample to drive the load 
connected to the motor. Since the torque de¬ 
pends upon the strength of the field and the 
strength of the armature current, the speed of 
motor increases till the counter E. M. F. re¬ 
duces the armature current to a value that 
gives just enough torque to drive the load. 
When a heravy load is thrown on the motor, the 
speed decreases. As the speed of motor 
decreases the counter E. M. F. decreases, per¬ 
mitting more current to flow through the arm¬ 
ature thereby increasing the torque. The speed 
of motor then decreases till the armature cur¬ 
rent reaches a strength that gives torque 



FIG. 284 


the same things as the generated E. M. F. 
in the armature of a generator,—strength of 
field, speed of armature, and manner arma¬ 
ture is wound. It increases with an increase 
in speed, and decreases with a decrease 
in speed, all other conditions remaining the 
same. It also increases with an increase in 
the field strength, if the speed remains the 
same, and decreases with a decrease of field 
strength, if the speed remains the same. Under 
normal conditions, the counter E. M. F. cannot 
equal or exceed the voltage of the circuit in 
which the motor is connected. 


enough to drive the load. If the load is made 
less, the speed of the motor increases, increas¬ 
ing the counter E. M. F. until the armature 
current is reduced to a value that gives just 
torque enough to drive the armature under the 
lighter load. 

Output of Motor 

The output of the motor depends upon its 
torque and the speed at which it is operating. 
If the torque is measured in foot-pounds, by a 
prony brake, and the speed in revolutions per 
minute is known, the output of the motor in 


/ 


















GENERATORS AND MOTORS 


291 


horsepower can be determined by the follow¬ 
ing formula. Output in horsepower 

6.2832 X lbs. x length of arm x R. P. M. 

^ 33,000 



PRONY BRAKE 

A. Motor pulley. C. Torque arm. 

B. Wooden clamping blocks. D. Spring scales. 


Operation of Shunt Motor 

When a motor having a shunt field winding 
is connected in circuit with a suitable source 
of E. M. P., current builds up through the shunt 
field coils and through the armature. The 
strength of the current in the shunt field coils 
depends upon their resistance and the voltage 
of the circuit. The current in the armature 
before the armature starts depends upon its 
resistance, and the voltage of the circuit. The 
torque produced by the reaction of the current 
in the armature coils on the field set up by 
the current in the field coils, causes the arma¬ 
ture to turn. As the speed of the armature 
increases the counter E. M. F. increases and so 
decreases the strength of the armature cur¬ 
rent. As the strength of the armature current 
decreases the torque becomes less. The speed 
of the armature then increases to a point where 
the torque is just ample to drive the load. The 
shunt wound motor does not have strong start¬ 
ing torque so it is not suitable for a starting 
motor. 

Operation of Series Motor 

When a series motor is connected in cir¬ 
cuit with a suitable source of E. M. F., current 
equal to the voltage of the circuit divided by 
the resistance of the motor is produced in the 
series field coils and the armature. The cur¬ 
rent remains at this strength for an instant 
only, since counter E. M. P. is generated, when 
the armature begins turning. As the counter 
E. M. F. increases with the speed of the arma¬ 
ture, the current is decreased in both the series 
field coils and the armature. As the current in 


the field coils and the armature decreases, the 
torque decreases, hence the speed of the motor 
increases till the torque is just ample to drive 
the load. The variation of the speed of a series 
motor is more than that of a shunt motor, 
when the load is varied, since the field coils are 
in series with the armature and the strength of 
the field varies as the armature current varies. 

Compound Motor 

The compound motor is a combination of 
the series and the shunt. The characteristics 
of the cumulative compound motor are be¬ 
tween those of the shunt and the series. A 
machine used as a starting motor is seldom 
compound, unless it is used as a generator also. 
If the machine is used as a motor-generator it 
runs as a cumulative compound motor, and a 
differential compound generator. 

Motor-Generators 

Some motor-generators have a double arma¬ 
ture winding and two commutators. The 
armature winding used when run as a motor 
is one made up of coils of few turns and heavy 
wire. These coils connect to the segments of 
the heavier commutator. The armature wind¬ 
ing used when run as a generator is made up 
of twice as many coils, each having more turns 
and wound with smaller wire. These coils 
connect to the smaller commutator which is 
made up of twice as many segments as the 
large commutator. Most of these machines use 
both field windings when run as a motor, but 
when running as a generator only the shunt 
field coils are used. The Delco motor-genera¬ 
tor is of this type. When the starting motor 
and generator is combined in one machine the 
starting and lighting system is usually called 
a single unit system. If separate machines are 
used for motor and for generator, the system 
is called a two unit system. 



FIG. 286 


REMY STARTING MOTOR EQUIPPED WITH BENDIX 

Characteristics of Starting Motors 

The starting motor must develop sufficient 
starting torque (twisting force) to “break the 
engine loose” even in the coldest weather, and 
sufficient power to drive the engine at a speed 
at which it will begin the cycle of operations or 



























292 


ADVANCED ELECTRICITY 


start. Series field coils are used on all starting 
motors to give them the necessary starting 
torque. Some starting motors have both series 
and shunt field coils; that is, are compound 
wound. If the starting motor is compound, it 
is always cumulative. 

Heavy current must pass through starting 
motors to give them the required starting 
torque and power. To carry this heavy current 
the series field coils are wound of heavy cop¬ 
per conductors, sometimes heavy copper rib¬ 
bon and the armature coils are wound of heavy 
copper conductors. Since the motor runs 
at comparatively high speeds there are usually 


few turns in the armature coils. The commu¬ 
tator is built up of heavy commutator seg¬ 
ments, usually much heavier than those used 
for the generator commutator. The brushes 
are sometimes copper plated to reduce their re¬ 
sistance. The resistance of the starting motor 
must be low, since the E. M. F. of the battery 
is not high enough to force the heavy current 
through much resistance. Where the four pole 
machine is used there are usually four brushes, 
even though the armature be wave wound. The 
extra brushes provide a greater area of contact 
on the commutator to carry the heavy current. 


ELECTRICAL AND MECHANICAL CON¬ 
NECTIONS OF THE STARTING 
MOTOR 

The electrical connection between the start¬ 
ing motor and the battery must be made 
through heavy conductors which have very low 
resistance. ,It is necessary to pass from 200 
to 400 amperes through six volt starting mo¬ 
tors to give them torque enough to break the 
engine loose and put it in motion and usually 
requires from 100 to 200 amperes to keep the 
engine turning after it is in motion. The 
strength of the current necessary to give a mo¬ 


tor the required torque, depends upon how hard 
the engine is to turn. The harder the engine is 
to turn the stronger the current must be, to 
give the motor the necessary torque. 

Divide 6, the number of volts a six volt bat¬ 
tery gives, by 300, the number of amperes re¬ 
quired to give a motor the necessary starting 
torque, and the quotient is 1/50, the maximum 
resistance the starting motor circuit can have. 
Therefore, if the resistance of the circuit is 
over 1 /50 of an ohm, the E. M. F. of the battery 
will not be strong enough to send sufficient 
current through the motor to give it the torque 


HORN AND TO JUNCTION PO«T FOR INTERIOR 
LIGHTING OF CLOSED CARS 


CIRCUIT RELAY 
TO SIDE LIGHT; 


DISTRIBUTOR 


RESISTANCE 
UNIT 



GROUND TO 
FRAME 


FIG. 287 

HUDSON—DELCO STARTING, LIGHTING AND IGNITION 























STARTING MOTORS 


293 


required for starting the engine. In fact, the 
resistance of the starting motor circuit must 
be kept under 1/50 of an ohm, as the battery 
does not give full six volts when discharging at 
a rate of 200 or 300 amperes. 

The conductors used to connect the bat¬ 
tery to the starting motor are usually in¬ 
sulated copper cables (No. 1 to No. 00 Brown 
& Sharpe Gauge). The connections are 
heavy and must be well made. The starting 
switch is also of heavy construction. The frame 
of the car is sometimes used for one side of the 
circuit. When the frame is used for part of 
the circuit, the ground connections must be 
heavy and well made. The construction of 
the starting switch varies with the different 


systems. The starting switches used on early 
systems are nearly all of complicated con¬ 
struction, but the tendency now is to make 
them of as simple construction as possible. 
Some do not even use a starting switch, but 
instead, lift the brushes of the starting motor 
off the commutator to open the circuit and 
lower the brushes onto the commutator to 
close the circuit. 

If the storage battery is moved to another 
part of the car where it is necessary to use 
longer cables to connect to the starting motor, 
proportionately larger cables should be used. 
On systems using twelve volt batteries it is 
only necessary to carry a current of one-half 
the strength that is necessary for six volt sys¬ 


tems. For this reason the cables connecting 
the battery to the starting ipotor are not as 
large. The starting motor is then constructed 
to work under twelve volts pressure instead of 
six. 

Mechanic2d Connections of Starting Motors 

Mechanical connection between the starting 
motor and the engine is made in several ways, 
varying with the different systems and differ¬ 
ent types of motors and motor-generators. 
Some machines which are used both as a motor 
and a generator are virtually built into the en¬ 
gine, the armature forming the flywheel as in 
the old U. S. L. installation, and some, the fly¬ 
wheel containing the held, as in the Owen 


Magnetic. These machines are large, and have 
armatures wound with coils of many turns, 
hence they turn at a comparatively low speed, 
and develop strong torque. 

Most motors and generators are built sep¬ 
arate from the engine, and connect mechani¬ 
cally to it through gears or a chain. (Some 
generators are driven by a belt, but belts are 
not used to connect starting motors to the 
engine.) 

The speed ratio between armature and 
engine on some installations is about 3 to 1. 
These machines are a little larger than the 
average, and have armatures wound with many 
coils, of many turns. They run at compara¬ 
tively low speed, and develop strong torque. 



NO 4 SPARK PLUG WIRE 


FIG. 288 

DODGE—NORTHEAST STARTING, LIGHTING AND IGNITION 

















294 


ADVANCED ELECTRICITY 


For example, the North-East motor-genera¬ 
tor used on th^ Dodge car connects to the 
engine with a silent chain. The speed ratio is 
3 to 1. When the machine runs as a motor, 
the armature turns under no load about 800 
R. P. M. When cranking the engine the arma¬ 
ture turns from 150 to 450 R. P. M. depending 
upon how hard the engine is to turn. Since the 
speed ratio is 3 to 1, the engine is driven 
from 50 to 150 R. P. M. 

When the engine starts its speed increases, 
hence drives the armature faster than it runs 
as a motor. With the engine running 500 R. P. 
M. the armature is then driven 1500 R. P. M. 
At this speed, a higher E. M. F. is produced 
than that of the battery and it has therefore 


to 1, to 40 to 1, it is necessary to have the me¬ 
chanical connection so made that when the en¬ 
gine starts, it cannot drive the starting motor. 
Unless some device is provided in the mechani¬ 
cal connection between the motor and the en¬ 
gine that will permit the engine to run without 
driving the motor, the mechanical connection 
is likely to be broken or the motor driven at a 
speed that will damage the armature when the 
engine starts. 

Overrunning Clutch 

Fig. 289, right, shows an illustration of the 
starting motor and the engine. (P) is a 
small pinion on the armature shaft. (I) is a 
larger gear meshing with (P) and is mounted 




changed automatically from a motor into a 
generator, and is charging the battery. The 
Dyneto motor-generator, as used on the Frank¬ 
lin, is much the same type of installation. 

Other motors have armatures wound with 
coils of comparatively few turns, so they run 
at high speeds, and do not develop very strong 
torque. These machines are small, and drive 
the engine through a comparatively high gear 
reduction, varying from 10 to 1, to 40 to 1. 

When a starting motor drives the engine 
through a gear reduction giving a speed ratio 
between armature and crankshaft from 10 


on the splined shaft (K). This shaft also 
carries the pinion (S) that is moved by the 
shifting fork (SF) to engage with the gear cut 
on the face of the flywheel (F). (1) is one of 

the four steel rollers carried in slots cut in the 
outer surface of the inner portion of the clutch. 
In each slot the depth varies, with the deepest 
part near the plunger (3), which has a small 
spring that prevents the roller from dropping 
back into the deeper part of the slot where it 
will not touch both inner and outer portions of 
the clutch. The inner portion of the clutch is 
keyed to shaft (K). 























































































































































STARTING MOTORS 


295 



GENERATOR 

SWITCH 


MOTOR 
COMMUTATOR 


UPPER MOTOR 
BRUSH 


OIL HOLE 


LOWER MOTOR 
BRUSH 


connects to 

TERMINAL (No. 2) 


CONNECTS TO 
NERATOR BRUSH 


PIN OPERATING MOTOR BRUSHES 


FIG. 290 

HUDSON—DELCO MOTOR-GENERATOR 
MOTOR COMMUTATOR END 


The operation as shown in the figure, is for 
pinion (P) to drive shaft (K) in a clockwise 
direction through the gear (I) of the clutch. 
As the pinion (P) drives gear (I), the steel 
rollers are caused to roll out into the narrow 
part of the slot, and so lock the ring to the 
inner portion of the clutch. If shaft (K) is 
driven faster than gear (I), the rollers are 
caused to roll back against the plungers into 
the wider part of the slots, releasing the inner 
portion of the clutch from gear (I). 

With the proper arrangement of this over¬ 
running clutch in the mechanical connection 
between the starting motor and the engine, 
the starting motor can drive the engine, and 
the engine can overrun the starting motor 
when it starts. This type clutch is used in 
practically all mechanical connections between 
the engine and the motor where sliding gears 
are meshed to make the connection. 

Fig. 289, left, shows a common type of me¬ 
chanical connection between starting motor 
and engine using sliding gears which are 
shifted by the starting pedal. The starting 
pedal connects to the sliding gear through the 
shift rod, spring, and shifting fork. When the 
starting pedal is pressed the gears are brought 
into mesh before the starting switch is closed. 
If the gears are in such position that the 
shift cannot be accomplished till one of the 



FIG. 291 

HUDSON—DELCO MOTOR-GENERATOR 
GENERATOR COMMUTATOR END 














296 


ADVANCED ELECTRICITY 


gears is moved a little, the spring behind the 
shifting fork, is compressed as the starting 
pedal is pressed. As soon as the pedal is 
pressed far enough to close the switch, the 
motor starts. A slight forward movement of 
the motor moves the pinion enough for the 
gears to be thrown quickly into mesh by the 
spring. 

Without the spring behind the shifting fork, 
the shift could not be accomplished at times, 
until one of the gears was moved a little. The 
spring must be strong enough to throw the 
gears into full mesh before the motor turns 


connection using a sliding gear (F), shifted 
by the starting pedal. The starting switch 
is so constructed that it closes the cir¬ 
cuit through the motor and the battery, 
through a resistance (A) when the starting 
pedal (B) is pressed part way down. This 
causes the motor to turn slowly, and with 
little power. Slowly turning gears are easily 
pushed into mesh as the pedal is pressed fur¬ 
ther forward, and the power of the motor, 
while the resistance is in series with it, is not 
enough to tear the corners from the teeth of 
the gears as they are brought into mesh. When 



far enough to take up the play, or the starting 
strain will come on the gears when only partly 
meshed, which is likely to cause them to be 
stripped. Another spring (return spring), pro¬ 
vided to bring the pedal back to neutral posi¬ 
tion, draws the gears out of mesh, and opens 
the starting switch when pedal is released. 

Fig. 292 shows another type of mechanical 


the pedal is pressed far enough down to fully 
mesh the gears, the starting switch shorts the 
resistance in series with the motor and then 
current of sufficient strength flows through the 
motor giving it the torque required to turn 
the engine. 

An overrunning clutch is carried in the slid¬ 
ing gear, which permits the engine to run 





























































































































STARTING MOTORS 


297 


i 


faster without driving the motor. When the ing gear at the end next to flywheel can easily 
starting pedal is released a spring throws it be pushed into mesh with gear on flywheel 
back to neutral position, drawing the sliding as the starting pedal is pressed, and the turn- 
gears out of mesh, and opening the starting ing force of the armature is not enough to 
switch, so that the motor stops. knock the corners off the teeth of the gears. 

The Delco motor-generators are connected When the starting pedal has been pressed far 
to the engine when running as a motor, enough down to slide the gears into full mesh, 
through sliding gears controlled by the start¬ 
ing pedal. These machines are of compara¬ 
tively heavy construction, and have armatures 
that are double wound and carry two commu¬ 
tators. One winding is made up of a single 
coil per slot, which is wound of heavy copper 
wire. This winding connects to the commu¬ 
tator segments of the large commutator. The 
other winding is made up of two coils per slot, 
wound of small wire, and many turns. This 
winding connects to the segments of the 
smaller commutator. The heavy winding 
is used when the machine runs as a motor, 
and the lighter winding when the machine 
runs as a generator. Instead of using a 
starting switch, the motor brushes are lifted 





When the ignition switch is closed, the gen¬ 
erator armature and shunt field are switched 
in circuit with the battery which forces cur¬ 
rent through them, causing the armature to 
rotate. Since the generator armature is of 
many coils and of small wires, the armature 
turns slowly, and with little force. The arma¬ 
ture is permitted to overrun the pump shaft by 
an overrunning clutch between the pump shaft 
and the motor-generator. 

With the armature slowly rotating, the slid- 


the motor brushes are forced down on the 
motor commutator, and the connection to the 
generator commutator is broken. On the 
Buick motor-generator the generator arma¬ 
ture connection is broken by raising the posi¬ 
tive generator brush. On others the connec¬ 
tion to the positive generator brush is broken 
by a switch arrangement on the brush holder 
of one of the motor brushes which is opened 
when the brush is forced down on the com¬ 
mutator. (See Figs. 290-291.) 











































































































298 


ADVANCED ELECTRICITY 



\ 











































































































































































































STARTING :M0T0RS 


299 


With the motor brushes on the commutator, 
the heavy series field coils, and the heavy 
armature winding are switched in circuit with 
the battery, and, being of low resistance, the 

E. M. F. of the battery causes a heavy current 
to flow through them that gives the armature 
torque enough to drive the engine through the 
sliding gears and the gear on the flywheel. 

An overrunning clutch is carried in the 
sliding gears to prevent the engine from driv¬ 
ing the armature at high speed when it starts. 
When the starting pedal is released it is drawn 
back to the neutral position by a spring, which 
draws the sliding gears out of mesh, raises the 
motor brushes off the commutator and at 
the same time, closes the switch making the 
connection to the positive generator brush. 
With the engine running, the armature is 
driven fast enough to generate a higher E. M. 

F. in the generator armature winding than 
that of a battery, hence the machine runs as 
generator and charges the battery. 

EUectromagnetic Shift 

Fig. 293 shows the principle of the electro¬ 
magnetic shift used on some of the West- 
inghouse starting motors. The soft steel 
shaft (E) passing through the hollow arma¬ 
ture shaft, shifts the drive pinion (C.) The 
solenoid (K) at the commutator end of the 
motor is a few turns of heavy wire, and is con¬ 
nected in series with the motor. When the 
starting switch (S) is closed, the heavy cur¬ 
rent passing through the solenoid sets up mag¬ 
netic lines of force that draw the shift rod 
through the hollow armature shaft, pulling 
the pinion into mesh with the gear on the fly¬ 
wheel. As soon as the engine starts, the load 
is thrown off the motor so that its speed in¬ 
creases and a stronger counter E. M. F. is 
generated. The stronger counter E. M. F. 
so decreases the current in solenoid that the 
sucking effect of the solenoid is not enough to 
hold the pinion in mesh against the snring that 
pushes the shift rod back to neutral position. 
When the pedal is released, a spring opens the 
starting switch and the motor stops. This 
system is sometimes equipped with a starting 
switch that is operated electromagnetically 
mstead of with the foot. A solenoid is pro¬ 
vided which is wound of many turns of small 
wire. This solenoid connects across the bat¬ 
tery terminals through a small push-button 
switch on the dash. When the ^button is 
pressed the solenoid is energized so the plun¬ 
ger operating the switch is drawn into it, clos¬ 
ing the starting switch. 


Bendix Drive 

Fig. 294 shows the Bendix drive. The 
pinion (P) is not keyed on the armature shaft 
but is carried on a heavy screw (T) which is 
mounted on the armature shaft or an inter¬ 
mediate shaft. When the starting switch is 
closed, by pressing the starting pedal, the 
motor starts very quickly. The pinion being 
heavy and weighted will not start to turn im¬ 
mediately but slips along the screw as the 
screw starts with the armature. The screw 
turning in the pinion pushes it along far 
enough to mesh with the gear on the flywheel. 
As the pinion meshes with the flywheel gear, 
it turns against the thrust collar at the end of 
the screw, which causes it to turn with the 
shaft, and so drive the engine. When the en¬ 
gine starts, it drives the pinion faster than the 
screw turns. The pinion overrunning the 
screw, is thrown back to the neutral position. 
When the starting pedal is released a spring 
opens the switch and the motor stops. The 
pinion is usually weighted on one side so it will 
not turn on the screw while the engine is run¬ 
ning and be thrown against the gear on the fly¬ 
wheel causing a clattering noise. If there is 
mud or gum on the Bendix, the pinion will not 
slip on the screw, so the gears will not be 
brought into mesh when the motor starts. 

A heavy strain is thrown on the gears 
just as the pinion turns against the thrust col¬ 
lar at the end of the screw, which is likely to 
strip the gear on the flywheel. This “jerk” is 
partly absorbed by the heavy Bendix spring 
through which the motor drives the screw. The 
Bendix spring should be coiled with the lay of 
the screw or the strain will break it. (See Fig. 
294 for correct and incorrect springs.) Instead 
of using the Bendix spring, some manufac¬ 
turers use a friction clutch. The clutch discs 
are held together with a spring, and the side 
thrust of the screw on the Bendix. The clutch 
slips enough at the start to prevent the “jerk” 
from breaking teeth out of the gear. 

The Bendix sometimes “jams.” This is 
usually caused by the starting motor being out 
of line with the crankshaft, or the pinion not 
meshing properly with the flywheel gear. The 
strong side thrust of the screw on the pinion 
forces the gears so tightly into mesh when 
the motor is not properly aligned that the 
engine cannot be turned. Sometimes a 
jammed Bendix can be loosened by putting the 
transmission in third speed and then rocking 
the car back and forth. At other times it may 
be necessary to knock the Bendix out with a 
hammer. When the Bendix jams, the starting 
motor should be realigned. 



300 


ADVANCED ELECTRICITY 


ELECTRICAL CONNECTIONS BETWEEN 
GENERATOR AND BATTERY 


The “charging circuit” includes the gen¬ 
erator, battery, usually an ammeter or an 
indicator, and a switch to open the circuit when 
the generator is not running so that the bat¬ 
tery cannot discharge back through the gener¬ 
ator. 

The ammeter is included in the circuit to 
indicate the strength of the charge or dis¬ 
charge of the battery. The ammeter, or 
battery indicator, is a trouble indicator. The 
ammeter indicates the strength of the 
charge current or the strength of the dis¬ 
charged current, while the indicator just indi¬ 
cates that the battery is being charged or is 
discharging. Figs. 311 and 312 show typical 
ammeters used in the charging circuit. Fig. 
313 shows a battery indicator. 

The switch used to open the circuit when 
the generator is not charging, may be hand 
operated or automatic. A good example of 
the hand operated switch is found in some 
of the Delco systems. In these systems the 
ignition switch opens the charge circuit when 
in “off” position and closes the circuit when 
in “on” position. The automatic switch is 
usually called the cut-out relay, though some¬ 
times called the cut-out, the circuit breaker, 
or reverse-current relay. 

The wire used for the charge circuit is 
usually about No. 14 insulated copper wire. The 
resistance of the charging circuits varies with 
the different systems but is usually about one- 
tenth of an ohm. The connections should be 
well made, since loose connections on some 
systems cause the generator voltage to rise, at 
high speeds, to a point that burns out the 
lamps or the ignition circuit. 

Cut-Out Relay 

Figs. 295, 296 and 297 show the fundamental 
construction of a cut-out relay. There are 
two windings, voltage and series, on the core 
of the electromagnet which automatically 
closes the relay. 

The voltage winding is of fine wire and many 
turns (500 to 1,500 turns) and is connected 
to the positive and negative terminals of 
the generator. The resistance of the voltage 
winding is often as high as 50 ohms. The 
series winding is of heavy wire and compara¬ 
tively few turns. The series winding together 
with the contacts is connected in series with 
the generator and the battery. The resistance 
of the series winding is very low, so low that it 
is practically negligible. 


Operation of Cut-Out Relay 

(See Fig. 295.) 

As a generator builds up, it forces current 
through the voltage winding. As soon as the 
generator voltage goes above that of the bat¬ 
tery, the current through the voltage winding 
reaches a strength that magnetizes the core 
strong enough to draw the contacts (C) to¬ 
gether against the tension of the spring (S) 
which tends to hold them apart. When the 
contacts close, the circuit through the genera¬ 
tor and battery is completed and the higher 
voltage of the generator causes an electric cur¬ 
rent to fiow through the battery in the direc¬ 
tion to charge it. The series winding is so 
wound and connected that the charge current 
fiows through it in the same direction as the 
current fiows in the voltage winding, hence 
assists the current in the voltage winding in 
magnetizing the core and holding the contacts 
together. 

When the generator voltage drops below that 
of the battery so that the battery discharges 
back through the generator, the current re¬ 
verses in the series winding, but not in volt¬ 
age winding, and thus partly demagnetizes the 
core so that the spring draws the contacts 
apart, opening the circuit. 

Adjustments on Cut-Out Relay 

There are two adjustments that can usually 
be made on a cut-out relay. The tension of 
the spring is first adjusted so that the contacts 
are drawn apart before the strength of the dis¬ 
charge goes above one ampere. (The contacts 
should separate when the strength of dis¬ 
charge is between zero and one ampere). 
Then the stop (see (A) in Fig. 296 and (B) in 
Fig. 297) against which the arm drops when 
the spring draws the contacts apart, is 
so adjusted that the contacts close on six volt 
systems when the generator generates be¬ 
tween 61/2 and 7% volts. On twelve volt sys¬ 
tems, the contacts should close when generator 
generates from 13 to 15 volts. If the contacts 
close too early, the arm does not drop back 
away from the end of the core far enough. If 
the contacts close too late the arm drops back 
away from the end of the core too far. 

Tests for Terminals of Cut-Out Relay 

(See Fig. 295.) 

There are three terminals on the cut-out 
relay. If the relay is used on systems using 
the frame of the car as one side of the circuit, 



REVERSE SERIES 


ELECTRICAL CONNECTIONS 


301 




oo 




FIG. 295 






































302 


ADVANCED ELECTRICITY 


(one wire system) one of the terminals is 
grounded. The terminal that grounds, (con¬ 
nects to frame) connects to one end of voltage 
winding, but not to the series winding. To 
distinguish this terminal from others it will be 
called terminal (G & B) imthe notes. Some cut¬ 
out relays used on one wire systems have this 
end of the voltage winding connected to the 
metal base, and so does away with terminal 
(G & B.) One terminal connects to both the 
series and voltage windings. This terminal is 
called terminal (G.) The terminal that con¬ 
nects to the series winding through the con¬ 
tacts is called (B.) 

The tests can be made best with a test lamp. 
Place the test points on two of the terminals 
of the relay. If the lamp lights and the con- 


points are on the terminals, the test points are 
on terminals (G & B) and (B.) Terminal (B) 
connects through the ammeter to the terminal 
of the battery that is not grounded. Terminal 
(G) connects to the generator terminal that is 
of the same polarity as the terminal of the bat¬ 
tery which connects to (B), and terminal (G 
& B) connects to other terminal of generator. 
The terminal of generator to which (G) con¬ 
nects must not be grounded. The terminal 
of generator to which (G & B) connects may 
or may not be grounded. 

REGULATION 

Regulation of a generator has to do with 
the automatic controlling mechanism, either 
mechanical or electrical, that prevents the 



FIG. 296 


CUT-OUT RELAY 


A. 

Stop which prevents bar from dropping back away 

E. 

Fiber block which insulates bar from stop. 


from core too far. Make air gap adjustment here. 

F. 

Contacts. 

B. 

Spring. 

G. 

Series winding. 

C. 

Battery terminal. 

H. 

Voltage winding. 

D. 

Generator terminal. 




tacts close, one of the terminals the test points 
are on, is (G) and the other is (G & B.) Ter¬ 
minals (G) and (G & B) must connect to the 
generator. Shift one test point to the third 
terminal on the relay. The lamp will not light 
now till the contacts are pushed together. If 
when the contacts are closed, the lamp lights 
and is bright the test points are on terminals 
(G) and (B.) If the lamp lights but is dim 
and contacts stay together as long as test 


generator from generating excessive voltage at 
high speeds. 

The automobile generator always has a 
shunt field winding and in addition to the 
shunt, some have the series field winding, and 
so are compounded. Practically all automobile 
generators are coupled to the engine, so that 
the speed of the armature varies with the speed 
of the crankshaft. A few of the earlier types 
(1914 and 1915) were driven through friction 











































CUT-OUT RELAY 


303 


clutches controlled by governor mechanisms 
for the purpose of regulation. These types 
now are practically obsolete. 

The automobile generator is usually de¬ 
signed to generate from 6 V 2 to 7 volts if used 
on systems with a 6 -volt battery, from 13 
tc 14 volts if used on systems with a 12-volt 
battery, when the car is running at a speed of 
from 71/2 to 10 miles per hour. This is neces¬ 
sary if the generator charges the battery 
at low engine speeds, as well as high engine 
speeds. When the speed of the car is increased. 



D 

FIG. 297 


A. Spring tension adjustment. 

B. Arm which prevents contacts from separating too 

far. 

C. Battery terminal. 

D. Generator terminal. 

the speed at which the armature is driven is 
increased correspondingly. As the speed of the 
armature increases the generated voltage in¬ 
creases. The voltage of a straight shunt 
generator increases almost with the square of 
the speed. Therefore if the generator was not 
regulated, it would generate high voltage at 
and above average running speed, so that parts 
of the system, such as the shunt field of gen¬ 
erator, voltage winding of cut-out relay, lamps, 
ignition coil, etc., would be burned cut. 

The cumulative compound generator builds 
up even faster with an increase in the speed 
than a straight shunt generator, hence is even 
less suitable for the automobile than the 


straight shunt generator. The straight series 
generator is in no way suitable for the automo¬ 
bile. Because of the demagnetizing effect of 
the current in the series field coils of the dif¬ 
ferential compound generator, it has a natural 
regulation that makes it suitable for use 
on the automobile. However, in some respects, 
the differential compound generator is un¬ 
suitable. 

The ideal generator for the automobile 
would be one which would give the same volt¬ 
age at all speeds of the car, and this voltage 
to be such that would force the current back 
through the battery at a rate that would just 
keep the battery in a fully charged condition. 
Such a generator as this is impracticable to 
build. Instead, generators regulated by some 
appliance to give about constant current, or 
constant voltage, are used. Regulation in¬ 
cludes the different appliances used to control 
the generator so that it will give about con¬ 
stant current, or about constant voltage. 

The strength of the E. M. F. (voltage) which 
a generator produces depends upon the way 
the armature is wound, speed of armature and 
the strength of field. Since the armature 
winding cannot be varied while machine is in 
operation, regulation must be accomplished by 
controlling the speed of armature or weaken¬ 
ing the field as speed of armature increases, 
and vice versa. 

Friction clutches carrying governor mech¬ 
anism for controlling the speed of the ar¬ 
mature so that the engine cannot drive it fast 
enough for generator to generate an exces¬ 
sive voltage, were used; but, since the facings 
of these clutches were worn very quickly— 
such clutches are slipping practically all the 
time at average engine speeds—this method 
of regulating generator was but little used. All 
other appliances for regulating the generator 
output weaken the field as the speed of the 
armature increases. 

The more important appliances for weaken¬ 
ing the field are as follows: 

(1) Reverse-Series Field Coils. Generators 
having reverse series field coils are those 
which are differential compound. 

(2) Vibrator Regulators. The vibrator 
regulator inserts resistance in series with the 
shunt field at higher armature speeds. These 
vibrators may be controlled by the current 
which the generator forces through the battery 
to charge it; by the voltage which the genera¬ 
tor generates; or by both the current and the 
voltage; or mechanically operated by cam on 
armature shaft. 

(3) Third Brush. 

Reverse-Series Field Coils 

Differential compound generators have an 


































304 


ADVANCED ELECTRICITY 


inherent or self-regulation, which is usually 
called “Reverse Series’’ or “Bucking Coil’’ 
regulation. (See Fig. 295.) The shunt field 
coils are so wound and connected that as 
the generator builds up from residual magne¬ 
tism, the current forced through them magne¬ 
tizes the poles stronger, and so sets up a 
stronger field. The series field coils are so 
connected that the current forced through 
them tends to demagnetize the poles. 

With the generator connected to a storage 
battery through a cut-out relay, there is prac¬ 
tically no current in the series field coils until 
the cut-out relay contacts close; but since the 
shunt field coils are shunted around the arma¬ 
ture, current builds up in them which strongly 
magnetizes the field poles, before the generator 



FIG. 298 

CUT-OUT RELAY AND IGNITION COIL MOUNTED 
ON GENERATOR—REMY 


builds up to high enough voltage to close the 
cut-out relay contacts. Therefore a strong 
field is built up before the speed of the arma¬ 
ture becomes high enough for the generator to 
begin charging the battery. As the speed of 
the armature is further increased, the genera¬ 
tor voltage rises high enough to close the cut¬ 
out relay contacts and force current through 
the battery in the direction to charge it. 

The voltage, so long as the battery is con¬ 
nected to generator, cannot rise more than a 
few volts above that necessary to close the cut¬ 
out relay contacts, since the current that is 
forced through the battery, flows through the 
series field coils tending to demagnetize the 
poles, hence weakening the field. Further in¬ 
creasing the speed of the armature will not 
cause the generator to force current through 


the battery at a much higher rate, as an 
increase in the current so weakens the field 
that even though the armature is turning at a 
higher speed, the armature conductors cut the 
lines of force at practically the same rate. 

The strength of the current which the gen¬ 
erator of this type forces through a battery 
depends largely upon the ratio between the 
number of turns in the shunt field coils and the 
number of turns in the series field coils. The 
field coils of generators are so wound at the 
factory that the machine will force the cur¬ 
rent through the battery at a rate that experi¬ 
ence has shown, will just about keep the 
battery charged. Should this charge rate be 
too low to keep the battery charged, because 
of unusual driving conditions, it will be neces¬ 
sary to have the battery charged occasionally 
at a service station. Or, if the charge rate of 
the generator is too high, so that it is over¬ 
charging the battery, it may be necessary to 
burn the lights, even in the day time, when 
making long trips. 

Under unusual conditions, the rate may be 
lowered by inserting a special resistance in 
series with the shunt field circuit of the gener¬ 
ator; or the rate may be increased by connect¬ 
ing a conductor in parallel with the reverse 
series field coil. In either instance the exact 
resistance to be used must be determined by 
experiment. 

Another method by which the output of a 
reverse series generator may be changed, is 
to change the number of turns in the reverse 
series field winding. Decreasing the number 
of reverse series field turns, increases the 
charging rate. Increasing the number of re¬ 
verse series turns, decreases the charging rate. 
When this method is used, the field coils must 
be rewound. Adding turns to the shunt field 
winding will not increase the charge rate. 

Some generators of this type—Bosch Rush- 
more, for example—have a small coil of iron 
wire connected in parallel to the series' field 
coils. This coil of iron wire is called ballast 
resistance. Since it is in parallel to the series 
field coil, part of the current which the gen¬ 
erator forces through the battery passes 
through it, instead of all going through the 
series field, consequently has no direct effect 
on the field. The part going through the 
ballast coil depends upon its resistance and the 
resistance of the series field coils. The higher 
the resistance of the ballast coil the less cur¬ 
rent passes through it, and the more passes 
through the series field coils. The lower the 
resistance of the ballast coil the more current 
passes through it, and the less passes through 
the series field coils. By changing the ballast 
coil to one of different resistance, the charge 
rate of the generator can be changed—if a coil 









GENERATOR OUTPUT REGULATION 


0 

u=d 


o 

O 

o 


■ 

Q 



305 



FIG. 299 






































































306 


ADVANCED ELECTRICITY 


of higher resistance is used, the charge rate is 
decreased, or if one of lower resistance is used 
the charge rate is increased. 

Generators having reverse series regula¬ 
tion give about constant current at average 
running speeds and so are called constant cur¬ 
rent generators. 

Vibrator Regulator—Current Type 

The vibrator regulator is a small appliance 
which weakens the field by intermittently in¬ 
serting resistance in series with the shunt 
field coils as the speed of the armature in¬ 
creases. When resistance is inserted in series 
with the shunt field coils, the current through 
them is weakened, hence fewer lines of force 
are set up in the field. 

The fundamental construction of the current 
type vibrator regulator is shown in Fig. 299. 
The regulator consists of an electromagnet, 
the winding of which is large wire and com¬ 
paratively few turns and is connected in series 
with the generator and the battery. 

A small bar of soft iron is mounted near 
one end of the core of the electromagnet 
and normally held away from the core by a 
spring. The contact carried on the soft iron 
bar is held against another contact by the 
spring which holds the bar away from the core 
of the magnet. A coil of several ohms resist¬ 
ance is connected in parallel to these contacts 
and the contacts are connected in series with 
the shunt field circuit. As long as the contacts 
are together, the coil of resistance is shorted 
by them hence the resistance of the shunt field 
circuit is practically the same as the shunt field 
coils. If the bar is pulled over against the core, 
the contacts are separated, and the coil of re¬ 
sistance is thrown directly in series with the 
shunt field coils, adding several ohms resist¬ 
ance to the shunt field circuit, which decreases 
the field current and therefore weakens the 
field. 

The operation of the regulator is as follows: 
As the speed of the armature increases, the 
strength of the generated E. M. P. increases; 
and, when it has reached a value ample to 
charge the battery, the cut-out relay contacts 
are drawn together, closing the charge circuit. 
The rate at which the generator forces current 
through the battery depends upon how much 
the generator voltage exceeds the voltage of 
the battery. As the generator voltage con¬ 
tinues to rise with an increase in the speed of 
the armature, the strength of the charge cur¬ 
rent increases. 

As the strength of the charge current in¬ 
creases, the core of the regulator is magnetized 
more strongly. When the charge current 
reaches a strength that magnetizes the core 
strongly enough to attract the bar against 


the tension of the spring, the regulator con¬ 
tacts are drawn apart, and the resistance coil 
is thrown in series with the shunt field. This 
added resistance in series with the shunt field 
coils so weakens the field that the generated 
E. M. F. drops to about that of the battery. As 
the generated E. M. P. drops, the strength of 
the charge current becomes less and the core 
of the regulator partly demagnetizes, permit¬ 
ting the spring to pull the bar away from the 
end of the core, and again close the contacts. 
When the contacts close, they short the resist¬ 
ance coil which was in series with the shunt 
field, and the generator again builds up to a 
voltage higher than that of the battery, forcing 
current through the battery. When the charge 
current again reaches a strength that mag¬ 
netizes the core strong enough to attract the 
bar against the tension of the spring, the regu¬ 
lator contacts are separated and the operation 
is repeated. 

The operation of the regulator is such that 
at speeds above that at which the generator 
forces a current through the battery strongly 
enough to just about magnetize the core and 
attract the bar, the bar will vibrate, inserting 
resistance intermittently in series with the 
shunt field. Intermittently inserting resistance 
in series with the shunt field coils in this man¬ 
ner, so weakens the field that the generator 
cannot generate a voltage higher than that 
which forces the current through the battery 
at the determined rate, even though the arma¬ 
ture be driven at a very high rate of speed. 
This regulator is called a constant current type 
regulator, since it so regulates the generator 
that it gives about constant current at average 
running speeds. 

The rate at which the regulator permits the 
generator to force current through the battery 
is determined by the tension of the vibrator 
spring. If the charge rate is too low, it can 
be increased by increasing the tension of the 
spring; if the charge rate is too high, it can be 
decreased by decreasing the tension of the 
spring. 

Vibrator Regulator—Voltage Type 

Pig. 300 shows the fundamental construc¬ 
tion of a vibrator regulator of the straight volt¬ 
age type. This type regulator differs from 
the current type regulator in that the winding 
on the core is of many turns of fine wire, and 
is connected in parallel to the battery. This 
type regulator gives about constant voltage 
regulation, since the strength of the current in 
the winding on the core depends directly upon 
the strength of the generator voltage and not 
upon the strength of the current passing 
through the battery. 

On systems using a 6 volt battery, the ten- 



GENERATOR OUTPUT REGULATION 


307 



FIG. 300 
























































































FIG. 301 





































































GENERATOR OUTPUT REGULATION 


309 


Sion of the vibrator spring is so adjusted that 
the current which flows through coil on the 
core when the generator voltage is from 714 to 
71/2 volts, magnetizes the core strong enough 
to draw the contacts apart. With this adjust¬ 
ment the regulator permits the generator to 
build up to 7^4: to 714 volts, but prevents it 
from building up to a higher voltage. 

Generators equipped with this type regu¬ 
lator are not likely to overcharge the battery 
since the back E. M. F. of the battery rise's 
to about that of the generator when the 
battery becomes fully charged. As the back 
E. M. F. of the battery rises, the difference be¬ 
tween the voltage of the generator and the 
voltage of the battery becomes less, since the 


in the series winding depends upon the 
strength of the charge current; and since there 
must be current in both the voltage and series 
windings to magnetize the core strong enough 
to draw the regulator contacts apart. 

The characteristics of this regulator lie be¬ 
tween those of the current and voltage types. 

Care and General Characteristics of Vibrator 
Regulators 

The charging rate of all systems using a 
vibrator type regulator may be changed by 
changing the tension of the spring that holds 
the regulator contacts together. 

Keep the contacts clean by the use of fine 
sand paper. 



voltage of the generator cannot rise beyond 
that which forces current through the coil on 
the regulator core at a rate that magnetizes 
the core strong enough to draw the contacts 
apart. 

Vibrator Regulator—Current-Voltage Type 

Fig. 301 shows the fundamental construc¬ 
tion of the current-voltage type regulator. This 
regulator is combined with the cut-out relay, 
so that the same windings and the same core 
can be used for both. This regulator is called 
current-voltage type, since the strength of the 
current in the voltage winding depends upon 
the voltage of the generator, and the current 


If the regulator contacts stick in a closed po¬ 
sition, the charging rate will be excessive. If 
they fail to close, the rate will be either very 
low, or will cut out altogether. 

If the resistance burns out, the contacts will 
become badly burned and often stick. 

Many vibrator regulators are equipped with 
two sets of contacts, which give longer life. 
In this case one set separates a little before the 
other. 

Field Distortion Regulation 

A general idea of field distortion produced 
by the reaction of the armature current on the 
field can be gained by comparing Figs. 302 











































































310 


ADVANCED ELECTRICITY 


and 303. In Fig. 302 the field is of uniform 
strength on both sides of the armature, but in 
Fig. 303 the lines of force are crowded to¬ 
wards the upper tip of the north pole and to¬ 
ward the lower tip of the south pole. This 
twisting of the lines of force out of their 
natural path is caused by the magnetic field 
set up by the current in the armature coils. 
The current sets up lines of force about 
the armature conductors which push the lines 
forming the field forward, distorting the field. 
The stronger the current in the armature coils 
the farther the lines are pushed out of their 
path, and the more the field is distorted. 


Illation, an odd brush, called the third brush, is 
added. One end of the shunt field connects to 
this brush, and the other end to one of the 
main brushes. The third brush is not placed 
on the point of commutation (neutral point) 
but instead, is placed around in the direction 
the armature turns, from the main brush that 
connects to the shunt field and near the other 
main brush. With this arrangement the cur¬ 
rent in the shunt field coils will become less as 
the field distorts, hence the field weakens. 

The manner in which the field is caused to 
weaken as the speed of the armature increases 
is described in general in the following. It is 



In* Fig. 302 it is assumed that the generator 
is running just fast enough to generate six 
volts, a voltage that is not high enough to close 
the cut-out relay contacts. The only current 
now passing through the armature is the shunt 
field current, which is comparatively weak, 
and not strong enough to distort the field to a 
noticeable extent. In Fig. 303 it is assumed 
that the generator is running faster, gener¬ 
ating about 71/2 or 8 volts, a voltage that is 
high enough to close the cut-out contacts, and 
charge the battery at about a 15 ampere rate. 
The current now passing through the arma¬ 
ture is 15 amperes plus the field current. Cur¬ 
rent fiowing through the armature at this rate 
is strong enough to distort the field consider¬ 
ably. 

When use is made of field distortion for reg- 


not possible to give in the description exact 
values for the E. M. F. in the armature con¬ 
ductors or the strength of the charge current, 
since Figs. 302 and 303 are merely illustrative 
and do not show as many armature conduc¬ 
tors as must be used in a generator. How¬ 
ever values have been given which will illus¬ 
trate the conditions in a generator having field 
distortion regulation while it is in operation. 

In Fig. 302 the speed of the armature 
is such that 6 volts are generated. The 
strength of the E. M. F. induced in the conduc¬ 
tors as they pass points (C), (D), (E), (F) 
and (G) are respectively about 1 / 0 , 11 / 2 , 2, lyo 
and 1/2 volts. The conductor while passing 
point (C), will not have as high an E. M. F. in¬ 
duced in it as when passing point (E), since at 
(C) it is not moving directly across the lines of 



































































GENERATOR OUTPUT REGULATION 


311 


force as it is at (E). These armature coils are 
in series, so their combined E. M. F. is equal to 
.their sum, or 6 volts, the force drawing the 
current through the armature from the nega¬ 
tive brush, and forcing it to the positive brush. 

The E. M. F. induced in conductors under 
north pole is equal to the E. M. F. induced in 
the conductors under the south pole to which 
they are diametrically opposite; hence the 

E. M. F. either side is the same. The force 
drawing the current from the third brush 
through the armature, and forcing it to the 
positive brush, is only the sum of the E. M. F.’s 
in the conductors passing points (C), (D) and 
(E), or 4 volts. Since the shunt field connects 
to the positive brush and the third brush, there* 
is an E. M. F. of 4 volts acting to cause current 
to flow through shunt field coils. 

When the voltage is increased by further in¬ 
creasing the speed of the armature, the cut¬ 
out relay closes and the generator forces cur¬ 
rent through the battery in the direction to 
charge it. When the armature reaches the 
speed at which the voltage is about 1^2 volts, 
the charge current is about 15 amperes. As the 
current of 15 amperes is drawn through the 
armature, the field is so distorted that the 
condition represented in Fig. 303 is produced. 
Since the lines of force are now crowded to¬ 
ward the top of the north pole and toward the 
bottom of the south pole, the conductors as 
they pass points (C) and (D), cut fewer lines 
than when passing points (F) and (G). The 
values of the E. M. F. induced in the conduc¬ 
tors now as they pass points (C), (D), (E), (F) 
and (G), are about i/4, %, 2, 2Vo and 2 volts re¬ 
spectively. Their combined E. M. F. is 71/2 
volts, which is the force drawing the current 
through the armature from the negative brush 
and forcing it to the positive brush. The E. 
M. F. drawing the current from the third brush 
to the positive brush is the sum of the E. M. 

F. in the conductors passing points (C), (D) 
and (E), or 3 volts. The force now drawing 
the current through the shunt field is less 
than before the field was distorted, hence the 
current in the shunt field is less and the field is 
weaker. 

Generators having this type of regulation 
usually reach their maximum output when the 
car is running about 25 miles per hour. At 
speeds above 25 miles per hour, the output 
falls off, because the field is then so weakened 
that less current in the armature distorts it to 
the point of regulation. 

If the battery is disconnected from a gen¬ 
erator of this type, the generator has no regu¬ 
lation and if run without battery will likelv 
burn out the field. If car is to be run without 
battery, either short the generator or open the 
field. 


The E. M. F. induced in the armature con¬ 
ductors as they pass the north pole is equal 
and opposite to that induced in them while 
passing the south pole, and assists in draw¬ 
ing the current through the armature from 
the negative brush to the positive. But, since 
with connection shown in illustration the cur¬ 
rent in the field coils is produced by the E. M. F. 
induced in armature conductors under the 
south pole, the right side of armature, was 
considered in the explanation. Practically the 
same results could be obtained were the third 
brush placed on the opposite side of commu¬ 
tator. The end of field coils which connects 
to positive brush in the figure, should then be 
connected to the third brush and the other 
end of field coils connected to the negative 
brush. 

The charging rate is increased by moving 
the third brush in the direction the armature 
rotates and is decreased by moving the third 
brush in the opposite direction to that in which 
the armature rotates. After shifting the 
brushes on any machine, whether a third 
brush, or main brushes, refit them to the sur¬ 
face of the commutator. 

Care of Commutator and Brushes 

By far the greater per cent of the troubles 
peculiar to motors and generators, is with 
the commutators and the brushes. If they 
are kept in proper operating condition other 
troubles are considerably in the minority. 
The commutator must be smooth, round and 
concentric to the shaft so that the brushes will 
ride on its surface and make a good contact. 

To true up a commutator, it should be placed 
on the centers of a lathe and the surface turn¬ 
ed off until it is accurate. The shape of the 
lathe tool is shown at the upper left in Fig. 
304. It should have a keen diamond shaped 
point of approximately the shape shown in the 
illustration. Light cuts should be taken until 
the surface is made accurate. When making 
the last or finishing cut, the tool should have a 
very keen edge and the cutting point should be 
rounded slightly with an oilstone. 

The finishing operation, after the final cut 
has been made, may be done with fine sand¬ 
paper. After the turning operation is com¬ 
pleted, the mica between copper segments 
should be “undercut.” The proper way to un¬ 
dercut the mica segments is shown at (C). 
The mica should not be undercut below the 
surface of the copper bars more than 1/32". 
This may be done with a piece of hacksaw 
blade with a suitable handle. (See (E) in Fig. 
304.) If the hacksaw blade is too thick to fit 
between the copper segments, grind the sides 
of the blade on an emery wheel. 

It is seldom necessary to undercut the mica 




312 


ADVANCED ELECTRICITY 


between the segments of starting motor com¬ 
mutators. Starting motors are used so little 
that trouble seldom arises from “high mica” 
in the commutator. 

Brushes should be fitted to a commutator by 
drawing a strip of sand paper between the 
brush and the commutator as shown at (D). 
There should be some pressure applied to the 
top of the brush to facilitate rapid grinding. 
Coarse sandpaper may be used to grind the 
brush to an approximate fit, after which No. 00 
sand paper should be used for the finishing 
process. 

GENERAL RULES AND SUGGESTIONS 

Keep the commutator round, smooth and 
free from oil and grease. 


Keep the brush spring tension sufficient to 
maintain proper brush contact at all times. 

Keep ALL connections clean and tight. 

See that the bearings are properly lubricated 
and not worn. 

Do not over-lubricate the bearings. Too 
much lubrication is sure to result in the com¬ 
mutator and brushes becoming gummed. 

See that the armature core does not drag on 
the pole pieces. 

TEST LAMP AND BUZZER 

A test lamp or test buzzer are often quite 
necessary for testing electrical equipment of 
all sorts, especially automotive equipment. 

The correct way to connect a test lamp is 
shown in Fig, 305. The most suitable pressure 


Side. 



Shajpe lathe tool. 
Saw 



Unctercutt iiy 


Brush. 


Wronj wa\j to undercut rnica 

c. 


FIG. 304 


ReJiitinj brush. 

0 , 


Keep the brushes free in their holders so the 
brush spring will keep them against the com¬ 
mutator. 

Keep oil and grease off the brushes. 

Keep dirt out of the grooves between the 
commutator segments when the mica is under¬ 
cut. 

See that the small flexible conductors 
(“shunts” or “pig tails”) are properly con¬ 
nected to the brushes and the brush holders. 


to use for a test lamp is 110 volts, and direct 
current is preferred. The lamp is in series with 
one of the conductors leading to the test points. 
If the circuit is a 220 volt circuit, both lines 
which lead to the test points should be cut and 
a 110 volt lamp connected in series with each 
test point. 

The internal circuit as well as the external 
wiring of a buzzer outfit is shown in Fig. 306. 
The buzzer has two binding posts (G) and (F). 

































GENERATOR OUTPUT REGULATION 


313 


One of the test points is connected directly to 
one of these binding posts. Four dry cells are 
connected in series to serve as a source of 
E. M. F. for the buzzer. The other test point is 
connected to one terminal of the dry cell bat¬ 
tery, and the remaining terminal of the battery 
is wired directly to the other binding post of the 
buzzer. 

The buzzer consists of a metal base upon 
which is mounted a U-shaped electromagnet. 
An armature of soft iron (A) is mounted upon 
a spring (B) near the poles of the magnet. A 
contact is attached to this armature by spring 
(H). This contact stands normally against 
the end of a screw (E). 

The operation of the buzzer is as follows; 
When the test points (K) are placed together, 
the electric circuit is completed and the current 


flows from the positive side of the battery to 
(F), through the two coils on the magnet core 
to (C), through spring (B) and (H), contacts 
(E) to (D), thence to (G), and through test 
points (K) to the negative side of the battery. 
This flow of current magnetizes the core of 
magnet, which then attracts armature (A), 
thus causing contacts (E) to separate. The 
separating of the contacts breaks the circuit 
and the core of the magnet becomes demag¬ 
netized. The armature is then drawn away 
from the core by the spring (B), closing the 
contacts; thus the circuit is again established 
and the operation is repeated. This device will 
continue to operate so long as the test points 
(K) are held together. A buzzer is very con¬ 
venient for testing circuits of few ohms resist¬ 
ance to determine whether they are complete 
or open. 




buzzer. 


Adjust rrteinfc 


Cells. 



, ,, Test Points. 

K 


FIG. 306 
















































314 


ADVANCED ELECTRICITY 


MISCELLANEOUS ELECTRICAL 
APPLIANCES 


Electric Horn 

There are several types of electric horns 
used on motor cars. The simplest is the vi¬ 
brating type. The construction of one type of 
vibrating horn is shown in Fig. 307. The 
mechanism consists of an electromagnet (J), 
near the poles of which is mounted an arma¬ 
ture (A) upon a spring (L) and bracket (H). 
The armature carries a contact (C), which 
normally closes the circuit through the magnet 
coils by resting against another contact 
mounted on bracket (G). Mounted between 
the flanges of the housing (K) and the mega¬ 
phone attachment is a diaphragm (D). In the 
center of this diaphragm is rigidly connected 
a post (B). One end of this post extends to a 
point near armature (A). 

The external circuit of the horn is completed 
by suitable conductors from (E), through a 
horn button (switch) and the battery, back to 
terminal (F) of the horn. 


The operation of the horn is as follows: 
When the circuit is closed by pressing the horn 
button, the current flows into the horn at (E), 
through the magnet winding, armature (A) 
contacts (C) and back to the battery. 

The flow of current magnetizes the core of 
the magnet (J), which attracts armature (A) 
and draws it towards the core. This separates 
the contacts (C), thus causing the magnet core 
to become demagnetized. When the core loses 
its magnetism, the contacts (C) again estab¬ 
lish the circuit and the operation is repeated. 

Each time the armature is drawn towards 
the magnet, it strikes the end of the rod (B), 
causing the diaphragm (D) to vibrate rapidly, 
this causing the sound. 

The Ford horn is illustrated in Fig. 308. 
The mechanism of this horn consists of an “E” 
shaped electromagnet (B) with a winding on 
the center leg of- the core. Near the poles of 
this electromagnet is a soft iron disc (G) fast- 














































ELECTRIC HORNS 


315 



to (F) it magnetizes the core in such a direc¬ 
tion that the pole over which the wire is wound 
becomes of north polarity and the two outside 
poles of the (E) shaped core of south polarity. 
The soft iron disc (G) will be attracted, thus 
drawing the diaphragm (H) towards the poles. 
When the E. M. F. wave of the magneto is fin¬ 
ished, the current in the coil of the horn ceases 
to flow and the core of the electromagnet be¬ 
comes demagnetized. When the core loses 
its magnetism, the iron disc being no longer 
attracted, moves away from the magnet. The 
induced E. M.'F. of the magneto reverses and 
the current then flows through the horn from 
(F) to (E). The pole of the core over which 
the wire is wound becomes of south polarity 
and the outside poles (one of them is marked 
(P) become of north polarity. The iron disc 




FIG. 309 


ened rigidly to a diaphragm (H). The circuit 
through the horn is from (E) to (F) through 
the magnet coil (C). The complete horn cir¬ 
cuit is from the magneto to (E), through horn 
winding (C) to (F), thence through a wire to 
the horn button (switch) and ground, through 
the frame of the car and back to the grounded 
end of magneto armature winding. 

To understand the operation of the Ford 
horn, it is essential that one should bear in 
mind that the Ford magneto produces an alter¬ 
nating current; that is, the current surges back 
and forth in the circuit. This horn will not 
operate on direct current. 

Operation of the Ford horn is as follows: 
As the current flows through the coil from (E) 


(G) is again attracted to the magnet, but as 
soon as the induced E. M. F. drops to zero, the 
current will cease to flow and the disc will move 
away from the poles. 

The operations described are repeated over 
and over each time the current alternates; 
thus, the diaphragm of the horn vibrates in 
synchronism with the alternations of the cur¬ 
rent, which accounts for the change in its tone 
when the speed of the engine is changed. 

Motor Driven Horn 

Fig. 309 shows the essential parts of a mo¬ 
tor driven horn. 

The motor which drives the horn is a minia¬ 
ture series wound motor of the two pole type. 


















































































316 


ADVANCED ELECTRIC I T Y 


The armature is shown at (A), the field poles 
at (L), the series field coils at (F) and the 
brush holders and brushes at (P) and (Q) 
respectively. (C) is the commutator. The 
armature is supported by the shaft (M). 
On one end of the armature shaft is a hardened 
steel rachet wheel (R). (D) is a diaphragm 

with a hardened steel cone shaped piece (B) 
mounted upon it and is held in place by screw 
(E) and lock nut (V). 

The circuit through the motor is from (S) 
to the upper field coil, through the coil and 
brush holder (P) to the commutator (C) and 
the armature. The current passes out of the 
armature at the lower brush, through the lower 
field coil and out at terminal (T). 

When the horn circuit is closed by pressing 
the horn button (switch), the armature (A) 
is caused to revolve, thus driving the ratchet 
wheel (R) at a high rate of speed. When the 
ratchet wheel impinges against the hardened 
steel piece (B) on the diaphragm, it causes the 
diaphragm to vibrate rapidly, emitting sound. 

Motor Horn Adjustments 

The adjustments for changing the tone of 
the motor driven horn are found either at the 
end of the armature shaft at (H) or within the 
megaphone at (E). The adjustments on the 
Klaxon are at (H) and on the Stewart at (E). 

If the armature of the horn motor revolves 
and the horn fails to emit sound, it is a surp 
indication that the ratchet wheel (R) does not 
strike the steel projection (B) on the dia¬ 
phragm. On the Klaxon the locknut (G) 
should be loosened and the armature bearing 
turned in or out, as the case requires, until the 
proper tone is obtained. On the Stewart the 
adjustment is made with a screw driver and a 
special wrench shown below the illustration 
of the horn. Loosen locknut (V) and turn 
screw (E) one direction or the other until the 
proper tone is obtained. After making adjust¬ 
ments be sure the lock nut is tightened. 

Plunger Type Ammeter 

Fig. 310 shows one of the simplest types of 
ammeters. It is called the plunger type meter. 
It consists of a case or housing in which is 
mounted a movable needle pivoted at (B). On 
the lower end of the needle is a soft iron 
plunger counter-balanced by a weight (W). 
The needle is held on the zero mark of the scale 
by a small spring which is similar to the hair 
spring of a watch. 

Between the two binding posts of the meter is 
connected a helix or solenoid (A) of the shape 
shown. When the current flows through the 
solenoid, a magnetic field is set up about it, 
which draws the plunger into the coil, caus- 



PLUNGER TYPE AMMETER. 

FIG. 310 


ing the needle to move across the scale. The 
scale is calibrated in such a manner that the 
amount of current flowing in the coil is indi¬ 
cated by the position of the needle. 

This type of meter may be designed to 
measure either alternating current or direct 



nOVABLE COIL AMPIETER. 


FIG. 311 






























































ELECTRIC HORNS — AMMETERS 


317 


current. It is seldom, if ever, used on the 
automobile. 

Movable Coil Ammeter 

The movable coil ammeter is illustrated in 
Fig. 311. It consists of a suitable housing with 
the meter mechanism within. The mechanism 
consists of a permanent magnet (C), between 
the poles of which is mounted a stationary core 
(D). Surrounding this core is a small coil of 
fine wire (E), which is pivoted at the center of 
the core (D) in such a manner that it is free to 
move. Needle (F) is secured to coil (E) so 
when the coil twists in the field, the needle is 
swung across a calibrated scale. The meter 
coil (E) is in parallel with a very low resistance 
shunt as shown. A very small per cent of the 
total current fiows through the meter coil (E), 
the greater per cent flowing through the shunt. 
The scale is so calibrated that the needle de¬ 
flections indicate the total current through the 
meter. A spring is depended upon to hold the 
needle on zero of the scale. 

Ammeters of this type are designed to operate 
on D. C. altogether, and will not operate on 
A. C. The ammeter, as applied to the automo- 






Roller. 

Battevjj Incticatov 

FIG. 313 


bile, is designed to indicate both charge and 
discharge, depending, of course, upon which 
way the current flows through it. 

The principles involved, which cause the 
meter coil to move and deflect the needle, are 
the same as the principles of the electric motor. 
When current passes through the coil, it is 
caused to twist proportionately to the strength 
of the current, the direction the coil twists de¬ 
pending upon the direction of the current. 


The Magnetic Vane, or Field Distortion Anunster 

The magnetic vane or distortion type amme¬ 
ter is shown in Fig. 312. 

It consists of a suitable case containing a 
permanent magnet (F), between the poles of 
which is pivoted an elliptical piece of soft iron 
(A). The needle is supported by the same 
pivot rod that supports piece (A). The needle 
is held on zero by the attraction of the magnet 
























































318 


ADVANCED ELECTRICITY 


for piece (A), holding it aligned between its 
poles as shown; that is, so that it forms a mag¬ 
netic path of low reluctance. 

(B) and (C) are the meter binding posts, 
between which are two parallel circuits (H) 
and (I). These two paths are of very low re¬ 
sistance. (D) and (E) are the poles of an elec¬ 
tromagnet, the coils of which are in the two 
circuits (H) and (I). 

The magnetism of the permanent magnet 
holds the soft iron piece (A) normally in the 
position shown. When current flows through 
the circuits (H) and (I), the poles (D) and (E) 
become magnetized and distort the magnetic 
fleld between the poles of the permanent mag¬ 
net, The soft iron piece (A) follows the dis¬ 
torted fleld and as a result, the needle moves 
across the scale. If the current through the 
meter is reversed, the field will be distorted in 
the opposite direction; hence, the needle will 
move across the scale in the opposite direction. 
This makes it possible to register both charge 
and discharge. 

The Battery Indicator 

The mechanism of the battery indicator is 
shown in Fig. 313. 

The right hand illustration shows the ap¬ 
pearance of the front of the instrument. The 
center illustration shows the drum which sur¬ 
rounds the small horseshoe magnet (A) in the 
left hand illustration. 

“CHARGE,” “OFF” and “DISCHARGE” are 
marked on the drum. The small horseshoe 

magnet in the illustration at the left is 

mounted in pivoted bearings, and near its poles 

is mounted a piece of soft iron (C). The at¬ 
traction of the poles for piece (C) causes the 
magnet to stand normally in the position 

shown. In this position no current is flowing, 
and the mark “OFF” appears in the opening 
in the front of the instrument. 

Between the binding posts (D) and (E) is a 
coil of wire (F). When the current passes 
through this coil, a magnetic field is set up, 
which is at right angles to the field of the ner- 
manent magnet (A). Magnet (A) will then 
turn so that its north pole points in the direc¬ 
tion the lines of force of the coil flow. When 
the current is reversed, the magnetic field about 
the coil also reverses; hence, the magnet (A) 
will turn in the opposite direction. The instru¬ 
ment indicates only charge, discharge or off; 
it does not indicate the amount of current 
flowing. It can be connected in the same man¬ 
ner on the car as the ammeter. 

The Automatic Ignition Switch 

Fig. 314 shows the mechanism of a typical 
Connecticut Automatic Ignition Switch. These 
switches are operated by a thermostat. 


The primary ignition circuit is as follows: 
When switch button (A) is pressed down, lever 
(I) drops into notch (F) and contacts (E) are 
closed. The current flows from the battery to 
(B), up through the contacts (E), then 
through the heater coil (L) and thermostat 
blade to (C), thence through the primary wind¬ 
ing of the coil and the breaker points to the 
ground, then to the grounded side of the bat¬ 
tery. 

If the ignition switch is left on when the 
breaker points are closed and the engine is not 
running, the current in the primary circuit be¬ 
comes greater than normal and heats the 
thermostat blade (M). As the temperature of 
the blade is increased, the blade bends upwards 
until contacts (K) are closed, at which time a 
circuit from the battery is completed through 
the coils (N) of a buzzer. The current in these 
coils causes the armature (P) to be attracted 
so that hammer (H) strikes trigger (Q), forc¬ 
ing lever (I) out of notch (F), thus opening 
contacts (E) and cutting off the flow of current 
through all parts of the switch. If the first 
stroke of hammer (H) does not release the 
switch, the buzzer mechanism continues to 
vibrate until contacts (E) separate. 

Pressure on push button (D) will cause 
spring (R) to be forced down, which will re¬ 
lease lever (I) from notch (F), allowing button 
(A) to move back and open contacts (E). A 
ground on the primary circuit causes more 
than normal current through the switch and 
will cause it to release. 

Later types of these switches operate with 
a double thermostat instead of a buzzer, mak¬ 
ing them practically noiseless. 

A thermostat consists of two blades of unlike 
metal, as (M) Fig. 314, usually brass and steel, 
either welded together throughout their entire 
length, or riveted together at their ends. Brass 
expands more than steel when heated; conse¬ 
quently, the blades will bend in such a direction 
that the brass becomes longer. In the illus¬ 
tration, the lower blade of the thermostat 
would be the brass blade and the upper one the 
steel blade. 

Any two metals having unequal expansion 
when heated can be used to form a thermo 
blade. 

The adjustment of the switch is made by 
changing the distance between contacts (K). 
The farther apart they are set, the longer the 
current must flow and the hotter the thermo¬ 
stat must become before the switch is opened, 
and vice versa. 

The Magnetic Gear Shift 

The principles of the magnetic gear shift are 
plainly set forth in Fig. 315. The operating 




AMMETERS — BATTERY INDICATOR 


319 



FIG. 314 


A. Switch button. 

B. Battery terminal. 

C. Ignition terminal. 

D. Release button. 

E. Switch contacts. 

F. Slot in which locking 
lever drops. 


G. Ground terminal. 

H. Hammer. 

I. Locking lever. 

J. Locking lever spring. 

K. Thermo blade contacts. 

L. Heater coil. 

M. Thermo blade. 


N. Electromagnet coil. 

O. Support for vibrator arm,. 

P. Vibrator arm. 

Q. Trigger, 

R. Release button spring. 

V. Vibrator contacts. 









































































































































320 


ADVANCED ELECTRICITY 


mechanism consists of a battery (H), a 
selector switch (G), four solenoid coils (A), 
(B), (C) and (D), two soft iron plungers (E) 
and (F), and a master switch (J). 

The master switch is controlled by the clutch 
pedal of the car. The selector switch is in 
easy reach of the driver. 

The solenoids and plungers are mounted on 
top of the transmission, the plungers being 
interconnected with the regular shifting bars 
of the transmission. When it is desired to start 
the car or to shift from one speed to another, 
the desired speed is selected by pressing the 
proper selector switch button. When the but- 


noid (A) and master switch (J). Under these 
conditions, coil (A) will be energized and 
plunger (E) drawn into it. 

The neutralizing mechanism is purely me¬ 
chanical and operates by pushing the clutch 
pedal half way down. This action draws the 
plungers (E) and (F) into the positions shown. 
The (N) button of the selector switch is to re¬ 
lease any of the switch connections made by 
pressing the selector buttons. The clutch 
should not be pushed all the way forward when 
driving, unless shifting gears. The clutch is 
properly disengaged when the clutch pedal is 
pushed forward a little more than half way. 



ton is pressed, a circuit is completed through 
the selector switch, thus throwing one of the 
solenoid coils in series with the battery, with 
the exception of the break in the circuit at the 
master switch (J). As soon as the clutch 
pedal is pushed all the way forward, the master 
switch is closed and one of the solenoids be¬ 
comes energized and the plunger is drawn into 
the coil, thus shifting the gears in the trans¬ 
mission. 

The circuit shown in the illustration is from 
the battery, through selector switch No. 1, sole- 


The arrangement of the solenoids and the 
selector switch connection is correct for an 
S. A. E. standard gear shift. The (A) coil is 
for low speed, the (B) coil is for reverse, the 
(C) coil is for third or high speed and the (D) 
coil is for second speed. 

LIGHTING 

Lzunp Bulbs, Sockets and Plugs 

The lamp ordinarily used on modern cars has 
a base known as the “Ediswan bayonet base.” 
This lamp base is shown in Fig. 316, upper 








































































321 


MISCELLANEOUS APPLIANCES — LIGHTING 


right. The base of the lamp has two small 
anchor pins which project about 1/16". These 
pins slide into suitable slots in the socket 
as shown. To insert the bnlb, engage the 
anchor pins in the slots, push bulb in as far as 
it will go, then turn slightly to the right. The 
spring plunger in the socket pushes the bulb 
outward, causing the anchor pins to lock the 
lamp into the socket. 

To remove the bulb, push in on it and turn 
slightly to the left. The lamp will then easily 
slide out of the socket. 

The left hand illustration sl\ows a double 
contact bulb and the type of socket re¬ 
quired. The base of the lamp has two con- 


One of the ‘‘leading in" wires of the bulb is 
connected to the base of the lamp and the 
other is connected to the single contact (C). 
The ground symbol and dotted line represent 
the frame return circuit. 

One should be certain when installing new 
lamp bulbs that they are designed for the 
socket into which they are being placed. If 
there are two contacts in the socket, the double 
contact bulb should be used. If there is only 
one contact in the socket, the single contact 
bulb should be used. 

The arrangement shown in the illustration 
at the left is used for leading in connections 
to the head light socket on a two wire system. 



FIG. 316. 


tacts, which connect to the filament of the 
lamp. The socket is equipped with two spring 
plungers which make contact with the two 
contacts on the base of the lamp when the bulb 
is properly installed. This type of socket is 
designed to be used in connection with a 
straight two wire system, but is used also in a 
number of instances in the single wire systems 
(ground system return). 

The illustration at the lower right is of the 
single contact lamp bulb and socket. This 
lamp and socket is used in the single wire 
systems. The socket has only one wire lead¬ 
ing to it, the return circuit being the ground. 


and to make the leading in connection for the 
two bulb (head and auxiliary) lights in a single 
wire system. 

Lamps—Sizes, Candle Power, Etc. 

There are two types of lamps that can be 
obtained for cars. These are known as the 
‘‘Mazda type B,” and the “Mazda type C.” The 
“Mazda type B" is a lamp from which the air 
has been exhausted. The filament is arranged 
in a double spiral order. The “Mazda type C” 
is a lamp from which the air has been ex¬ 
hausted and nitrogen gas substituted in its 
place. The filament is arranged in a “V" shape. 












































































322 


ADVANCED ELECTRICITY 


The “Mazda type B” consumes about 1 
watts per candle power and the “Mazda type 
C” about 1 watt per candle power. The type 
“C” lamp is, therefore, the more efficient. 
Lamps of either the “B” or “C” type can be 
obtained for any range of voltage used on cars. 

Methods of Dimming Headlights (Electrically) 

The four methods used for obtaining dim 
headlights are as follows: 


Focusing Headlights 

The lower illustration in Fig. 318 shows a 
section through a parabolic reflector. A 
straight line drawn through the center of the 
lens and the apex of the reflector is called the 
axis of the reflector. 

The source of light (the filament of the 
lamp) should always be on this line. The 
focal point is a point on this line where the 




(a) By changing the lights from a parallel 
connection for bright to a series connection 
for dim. 

(b) By inserting resistance in series with 
the headlights. 

(c) By the use of auxiliary headlights. The 
main headlights, which are usually of high 
candle power and placed in the focus of the 
reflector, are turned off and small candle power 
bulbs, which are out of the focus of the re¬ 
flector, are turned on. 

(d) By using a bulb equipped with two fila¬ 
ments of different candle power, either of 
which may be placed in use by turning light¬ 
ing switch to the proper position. 

The first three methods are shown in Fig. 
317, in the same order as described above. 



FIG. 318 























































































LIGHTING 


323 


source of light should be placed, as at (F), in 
order that the reflected light will be projected 
ahead of the car in parallel rays, indicated by 
the parallel lines marked (F). If the source 
of light is placed ahead of the focal point, as 
at (A), the reflected light will be in the direc¬ 
tion of the line (A), which crosses the axis. 
When the source of light is back of the focal 
point,-as at (B), the reflected light will form a 
diverging pencil of light, as indicated by the 
long line (B). 

To focus the lamps, place the car so that the 
lights strike squarely against a light colored 
wall 40 to 75 feet ahead of the car. Adjust the 
bulbs by moving them either forward or back¬ 
ward along the axis until the proper spot on 
the wall is obtained. The spot should not be 
less than 3i/^ feet in diameter and should be 
free from dark rings. Tip the headlights for¬ 



ward at the top if possible so that the light will 
be thrown on the road. This can be done in 
some instances by bending the head lamp 
brackets. 

The two upper illustrations. Fig. 318, show 
two common points at (A) where the lamp 
focusing adjustments are located. On some 
cars, as the Ford and Overland “4,” a small 
screw is located on the outside of the lamp 
housing just above the ajiex. Turning the 
screw at this point moves the lamp along the 
axis of the reflector. 

Care of Reflector 

Never allow the fingers to touch the silvered 
surface of a reflector. 


Dust may be removed by a stream of clean 
water from a hose, but do not allow the water 
to strike the surface under pressure. 

Jeweler’s rouge and a perfectly clean cham¬ 
ois skin, or a wad of absorbent cotton moist¬ 
ened with alcohol, may be used to clean a 
reflector which is badly tarnished. 

ARMATURE TESTING 

Fig. 319 illustrates a few common tests made 
on armatures. Tests (B), (C), and (D) apply 
particularly to Delco motor-generator arma¬ 
tures which have two sets of armature wind¬ 
ings and two commutators, although tests (C) 
and (D) apply equally well on other armatures. 
The test shown at (A) is to determine in a 
rough way whether an armature is shorted or 
open circuited, without removing the dynamo 
from the car. See that the commutator is 



clean and in good condition, open the shunt 
field circuit and connect a sensitive ammeter 
in series with the armature and a good dry cell. 
Note the reading of the ammeter. Turn the 
armature slowly, watching the ammeter 
closely. If the armature is in good condition, 
there should be only a slight variation in the 
reading, if any at all. If there is quite a varia¬ 
tion, the armature is either open or short cir¬ 
cuited. This test will not determine the nature 
of the trouble. 

The test at (B) is to determine if there is a 
short circuit between the motor and the gen¬ 
erator windings of a Delco motor-generator 
armature. These windings normally have no 


v__i_ 

FIG. 319 























































ADVANCED ELECTRICITY 


324 


C/J 

























































ARMATURE TESTING 


connections from one to the other. If the test 
lamp lights, the motor and generator windings, 
because of a break in the insulation, are 
touching and thus short circuited. 

The test at (C) is to determine if the gen¬ 
erator windings or commutator are grounded. 
If they are not grounded, the lamp should not 
light. 

The test shown at (D) is for the motor 
winding. 

Bar to Bar Test 

The tests shown in Fig. 320 are called 
“bar to bar” tests to locate shorts or opens in 
an armature. The meter used for these tests 
should be very sensitive and capable of quite 
a range. A millivoltmeter is required as a rule 
to make the test for shorts. 

The test points of the meter are preferably 
made of steel and have keen points which may 
be pricked into the copper commutator bars, 
insuring a perfect contact. 

Connect a bank of headlight bulbs, a six 
volt storage battery and the armature to be 
tested, in series as shown. The wires connected 
to the commutator bars should be soldered to 
them, to insure that there will be no variation 
in the flow of current. The lamps control the 
flow of current through the armature, as the 
armature resistance alone is usually too low 
to limit the current to a suitable strength. 

The test for open circuits should always be 
made first, then the tests for short circuits 
should follow. If the test for shorts is made 
first and an open exists in the armature wind¬ 
ing, the meter will be more than-likely burned 
out, when it is connected across the bars of the 
commutator to which the open coil is con¬ 
nected. 

The 30 volt scale may be tried out first and 
if the deflection from bar to bar is less than 3 
volts, the 3 volt scale may be used. If it is 
found when the 3 volt scale is used, that the 
deflection of the meter needle when the instru¬ 
ment is connected from bar to bar is less than 
.1 volt, then the .1 volt scale may be used. 
The connections for the 30 volt scale is indi¬ 
cated in full lines. The 3 volt and .1 volt 
scale connections are shown in broken lines. 
The wire on the meter terminal marked 30 
should be transferred to either the terminal 
No. 3 or .1, depending upon the scale to be 
used. The wire on meter terminal marked 
with the positive sign should never be changed. 
When the 30 volt scale is used the full scale 
of the instrument is 30 volts. When the 3 volt 
scale is used, the full scale of the instrument 
is only 3 volts, etc. 

When making the bar to bar test for shorts 
(when no opens or shorts exist) there will be a 
circuit through each side of the armature from 


325 


(K) to (A). The total pressure which acts be¬ 
tween (K) and (A), acts equally on both sides 
of the armature. The voltage acting across 
each of the armature coils is equal to the volt¬ 
age across (K) and (A) divided by the number 
of armature coils between these two points. In 
the illustration we have 12 coils in each side 
of the armature between the two points, hence 
1/12 of the pressure between (K) and (A) 
acts upon each of these coils. In the bar to 
bar test the meter should register 1/12 of the 
total pressure between (K) and (A) across 
each of the armature coils, if they are in good 
condition as in the left side of the armature. 

Test for Opens 

With the circuit connected as shown, it is 
evident that current will flow from (K) to (A) 
through the left side of the armature and that 
no current will flow through the right side of 
the armature, as the armature coil between 
(F) and (G) is open. 

A bar to bar test around the right side of the 
armature will give no reading on the meter 
until the meter is connected across the two 
bars between which is the open circuited 
coil. When the meter is connected across the 
two bars (F) and (G), a reading equal to the 
pressure acting between segments (K) and 

(A) is obtained. 

If the armature resistance is equal to the 
resistance of the lamps, one-half of the full 
pressure of the battery would be registered by 
the meter. The higher the joint resistance of 
the bank of lamps in proportion to the resist¬ 
ance of the circuit through the armature, the 
lower the reading on the meter. The lower 
the resistance of the bank of lamps in propor¬ 
tion to the resistance of the armature, the 
higher the reading of the meter. The joint 
resistance of the lamps may be decreased by 
increasing the number of lamps in parallel. 

Test for Short Circuited Armature Coil 

The test for short circuited armature coils 
illustrated at right is practically the same as 
the test for open circuits, with the exception 
that a different meter scale may be required. 

In the right side of the armature it should be 
noted that one of the armature coils is short 
circuited, leaving only 11 coils in this side of 
the armature, hence 1/11 of the total pres¬ 
sure between (K) and (A) would act upon 
each of these coils. 

When making the bar to bar test equal de¬ 
flections of the meter needle should be 
obtained across all of the points, (A) to (B), 

(B) to (C), etc., until the test from (G) to 
(H) is made. The deflection across these 
points will be practically zero, as the resistance 
of the coil between these points is shorted out 
of the circuit. 






326 


ADVANCED ELECTRICITY 


SUMMARY 


GENERATORS 

A generator is a machine which converts 
mechanical energy into electrical energy. The 
generator as applied to automobiles is always 
of the revolving armature type. The field 
magnetism is produced by electromagnets in¬ 
stead of permanent magnets as in the mag¬ 
neto. The term “dynamo” is used to designate 
either a generator or a motor. 

There are three distinct types of generators 
and motors — series wound, shunt wound 
and compound wound. The compound type is 
subdivided into the “cumulative compound” 
and the “differential compound.” 

The cumulative compound is a machine in 
which the magnetizing effect of both the 
series and shunt field windings tend to mag¬ 
netize the field poles of the same polarity. In 
the differential compound machine the series 
and shunt field windings tend to magnetize the 
field poles oppositely, that is, the series field 
and the shunt field coils oppose each other. 

The type of generator or motor is always 
determined by the type of field windings and 
not by the armature. 

ARMATURE 

The armature of a generator or motor may 
be of either the ring or drum wound type, al¬ 
though there are at present no ring wound 
armatures used in automobile equipment. 

Drum windings are sub-divided into the lap 
winding and the wave winding. Lap windings 
can be used on any motor or generatpr, but the 
wave winding can not be used in two pole 
machines. 

In four pole machines using lap wound arma¬ 
tures, there are as many brushes resting upon 
the commutator as there are field poles, but 
with the wave wound armature there may be 
only two brushes resting on the commutator, 
in which case brushes are spaced around the 
commutator 90 degrees one way and 270 de¬ 
grees the other. 

There are as many magnetic circuits 
through a lap wound armature as there are 
brushes on the commutator. There are only 
two through a wave wound armature. 

THE NEUTRAL POINT 

The neutral points of a generator or motor 
are the points at which the armature conduc¬ 
tors move parallel to the path of the magnetic 
lines of force. 

The neutral points of a generator are for¬ 
ward in the direction of rotation from a point 
half way between the field poles. The neutral 


points of a motor are slightly back of the 
points half way between the field poles, oppo¬ 
site to the direction of rotation. If a generator 
is producing voltage only and not delivering 
current, the neutral points will be midway be¬ 
tween the field poles. The reaction of the mag¬ 
netism produced by the current in the arma¬ 
ture causes the field magnetism to be distorted. 

The brushes should be set on the commuta¬ 
tor so that they short circuit the armature coils 
as the coils pass the neutral points. 

The points of commutation of a generator 
are the points at which the brushes rest when 
the generator produces the greatest output at 
a given speed, with the least sparking at the 
brush contact on the commutator, the com¬ 
mutator, brushes, etc., being in good condi¬ 
tion. 

The points of commutation of a motor are 
the points at which the brushes rest on the 
commutator when the motor will develop its 
greatest torque, with a minimum consumption 
of energy and with the least sparking at the 
commutator and brush contacts, the commu¬ 
tator, brushes, etc., being in good condition. 

MOTORS 

An electric motor is a machine that converts 
electrical energy into mechanical energy. 

The electric motor is designed in practically 
the same way as the generator. Either of the 
machines will operate as the other, although 
the details of the two machines vary, because 
of the difference in the work they are re¬ 
quired to do. 

The single unit systems are a compromise 
between the regular generator and starting 
motor design. 

Series wound machines are used as starting 
motors only, with the exception of their ap¬ 
plication to driving the signal horn. 

Shunt machines are used on cars as genera¬ 
tors only. 

Compound machines have the combined 
characteristics of the series and shunt ma¬ 
chines, hence this type is used as a motor- 
generator. When this machine is operated as 
a motor, it operates as a cumulative compound 
machine; when operated as a generator, it 
operates as a differential compound machine. 
There are exceptions to this rule. 

GENERATOR DRIVES 

Generators are sometimes driven by means 
of a belt and in other instances by a silent 
chain; still, in other instances they are driven 
by means of suitable gearing. 




SUMMARY 


327 


See that the belts do not slip when belt 
driven. 

MOTOR TO ENGINE MECHANICAL 
CONNECTIONS 

The most common motor to engine mechani¬ 
cal connections are as follows: 

(1) Chain and sprockets, with an over¬ 
running clutch. 

(2) The manual gear shift, with an over¬ 
running clutch. 

(3) The Bendix drive. 

REGULATION 

Regulation of the generator output is neces¬ 
sary- to prevent the generator from overload¬ 
ing itself and from charging the battery at an 
excessive rate, at high speeds. 

With generators having electromagnetic 
field poles the voltage builds up very rapidly as 
the speed increases. The increase, in voltage 
in some cases is proportional to the square of 
the speed, according to the field winding. 

The voltage of a generator depends upon the 
number of active armature conductors, the 
strength of the magnetic field and the speed of 
the armature. 

The number of armature conductors are de¬ 
termined by the manufacturer and the speed 
of the generator depends upon the speed at 
which the engine runs, hence these two factors 
can not be easily changed. 

The strength of the field can be easily 
changed, consequently, advantage is taken 
of this and the result is that the gen¬ 
erator voltage is regulated by a variation of 
field strength. The generator field magnetism 
is decreased (weakened) as the engine speed 
increases, thus maintaining a more nearly con¬ 
stant output. 

There are several methods of regulation em¬ 
ployed on modern electrical systems, among 
which are: 

(1) Reverse-series field regulation. 

(2) Regulation by vibrating type regulator. 

(3) Field distortion or third brush regula¬ 
tion. 

The charging rate of a reverse series regu¬ 
lated generator can be decreased, by inserting 
a resistance unit in series with the shunt field 
circuit of the generator. To increase the 
charging rate, a conductor should be con¬ 
nected in parallel with the reverse series field 
winding. These changes in the charging rate 
are made by experimenting, as there are no 
set rules to follow regarding the resistance to 
use in either case. 

To increase the charging rate on a system 
equipped with a vibrating type regulator, in¬ 
crease the tension of the spring that holds the 
regulator contacts closed. 


To decrease the rate, decrease the spring 
tension. 

To increase the charging rate on a system 
where the generator has field distortion or 
third brush regulation, move the third brush 
in the direction of armature rotation. 

.To decrease the rate, move the brush in the 
direction opposite to the armature rotation. 

It is not recommended that the charging rate 
be changed until sufficient test has been made 
showing it to be incorrect; one should always 
be sure that everything else is in good condi¬ 
tion before changing the charging rate. 

CUT-OUT RELAY 

The cut-out relay is an automatic switch in 
the charging circuit of an electrical system. 

The purpose of the cut-out relay is to close 
the charging circuit when the voltage of the 
generator is slightly in excess of the voltage of 
the battery, and to open the charging circuit 
when the voltage of the generator drops 
slightly below the voltage of the battery. 

The cut-out relay consists of an electromag¬ 
net which is compound wound, and a set of 
contacts in series with the charging circuit. 
These two windings are called the voltage and 
series windings. The voltage winding is some¬ 
times referred to as a shunt winding. 

The purpose of the shunt winding is to close 
the relay contacts. The purpose^ of the series 
winding is to cause the relay to open. 

The cut-out relay should close at a pressure 
of 6 y 2 to 7%, volts on six volt systems and 
13 to 15 volts on twelve volt systems. 

The cut-out relay should open when the dis¬ 
charge current is as near zero as possible, 
usually one ampere or less. 

There are usually two adjustments on a cut¬ 
out relay; these adjustments are: 

(1) Spring tension. 

(2) Air gap. 

The air gap and spring tension control the 
closing of the cut-out relay. 

The spring tension controls the opening. 

In making adjustments, it is advisable first to 
make them roughly, then to make the final ad¬ 
justments. The opening adjustment should 
be made first, by changing the spring tension. 
If the relay then closes incorrectly, the air gap 
should be changed until the correct closing is 
obtained. 

Keep the contacts clean and adjusted so that 
they strike squarely together. 

ELECTRIC HORNS 

There are three types of electric horns in 
common use, as follows: 

(1) The ordinary type vibrating horn. 

(2) The Ford vibrating horn. 

(3) The motor driven horn. 





328 


ADVANCED ELECTRICITY 


The Ford vibrating horn will operate only on 
alternating current, such as is obtained from 
the Ford Magneto. See main text for adjust¬ 
ments and full descriptions of construction and 
operation. 

DIMMING HEADLIGHTS 

There are several methods used to dim the 
headlights; some are of a mechanical nature, 
while in others the lights are dimmed elec¬ 
trically. 

The mechanical methods consist of special 
shutters, special lenses, special reflectors, etc. 


When dimmed electrically, it is usually ac¬ 
complished in one of the following ways: 

(a) By changing the headlights from a 
parallel connection for bright lights, to a series 
connection for dim lights. 

(b) By inserting a special resistance in 
series with the headlights. 

(c) By the use of small bulbs called auxil¬ 
iary headlights, placed out of the focus of the 
reflector. 

(d) By having a bulb equipped with a 
double filament, one of high candle power and 
the other of low candle power. 


QUESTIONS 


144. What is a dynamo? 

145. Is there any difference between a 
motor and a generator? 

146. What is meant by the field of a motor 
or generator? 

147. What is the armature of a motor or 
generator? 

148. What is the purpose of the armature 
core? Of what material is the core made? 

149. What is a commutator? What is its 
purpose? 

150. What is the fundamental difference 
between the ring wound armature and the drum 
wound armature? 

151. How many brushes are necessary for a 
four pole lap wound armature? Four pole 
wave wound armature? 

152. What are the general requirements of 
a starting motor? 

153. Why are series field coils necessary on 
starting motors ? 

154. Why are large conductors necessary 
for connecting the starting motor to the 
engine. 

155. Name and describe four mechanical 
arrangements for connecting the starting 
motor to the engine. 

156. What causes the Bendix pinion to jam? 

157. What is an overrunning clutch? 
Where is it used and for what purpose? 

158. Why do some starting switches have 
a resistance coil placed in them? 

159. Explain how shunt field coils differ 
from series field coils. 

160. What appliances are included in the 
charging circuit? 

161. What is a cut-out relay? 

162. How many windings has a cut-out 
relay? 

163. Is there any difference in the wind¬ 
ings? 


164. What are their purposes? 

165. How many terminals has a cut-out 
relay? 

166. To what do the terminals connect in 
the charging circuit? 

167. How is the cut-out relay tested? 

168. Through which winding is current 
passed to close the cut-out relay? 

169. How do cut-out relay points normally 
stand? 

170. Does the current flowing from the 
battery close or open the points on cut-out 
relay? 

171. Do cut-out relays have electromag¬ 
nets? 

172. What causes the cut-out relay points 
to open after they have been closed? 

173. At what voltage should the relay points 
close? 

174. What is used to find at what voltage 
the cut-out points close? 

175. If points close late what adjustment 
should be made? 

176. Should a buzzer close the cut-out 
contacts in testing if the points are adjusted 
to close properly? 

177. Where and what kind of an instrument 
should be inserted to determine the strength 
of discharge of the battery at the time con¬ 
tacts open? 

178. Is the cut-out relay to keep the battery 
from overcharging? 

179. What causes cut-out relay contacts to 
burn? 

180. What can be inserted to protect these 
contacts? 

181. How many adjustments on a cut-out 
relay? 

182. What controls the opening? What 
controls the closing? 

183. If a cut-out relay closed at 9 volts and 






A D A N C E D ELECTRICITY 


329 


opened at 3 amperes discharge what adjust¬ 
ment should be made? 

184. What method can be taken to deter¬ 
mine whether or not the voltage winding of the 
cut-out relay is open? 

185. What is meant by the term “regula¬ 
tion”? 

186. Why is regulation of the generator 
necessary? 

187. How is regulation of the automobile 
generator accomplished? 

188. How many field windings are there in 
a generator having a reverse-series regulation? 

189. Will generator of this type charge 
battery if the shunt field is open? If series 
field coils are shorted? 

190. What effect do corroded battery ter¬ 
minals have on systems using generator of this 
type? What is the effect of loose connections 
in the charging circuit? 

191. How can the charging rate of a gener¬ 
ator of this type be increased? Decreased? 

192. Explain how a vibrator regulator con¬ 
trols a generator. 

193. Do the vibrator regulator points nor¬ 
mally stand open or closed? 

194. What causes the vibrator regulator 
points to stick? How could this affect the out¬ 
put of the generator? 

195. How could a combined current and 
voltage type regulator be distinguished from a 
current type regulator? 

196. How could a voltage type regulator be 
distinguished from combined current and vol¬ 
tage type regulator? 

197. Do all three types of vibrator regula¬ 
tors affect the same circuit of the generator 
for regulation? 

198. How can a vibrator regulator be dis¬ 
tinguished from a cut-out-relay? 

199. What would be the difference in the 
sound of buzzer if testing between the genera¬ 
tor positive terminal and shunt field terminal 
if the regulator points are open? 

200. Do regulators have electromagnets? 

201. Why is the resistance of a regulator 
sometimes divided? 

202. Will a regulator keep the generator 


from overcharging a battery when batterv tests 
1.300? 

203. With a combined current and voltage 
type regulator does the series winding assist 
the voltage winding or act in opposition to it 
after the cut-out points close? 

204. What will indicate the spring tension 
has been increased too much? 

205. Why do regulator points sometimes 
have a condenser across them? 

206. How could the generator with vibrat¬ 
ing type regulation be distinguished from a 
generator with reverse series or field distor¬ 
tion regulation? 

207. What is field distortion? What causes 
it? 

208. Explain how field distortion is used to 
regulate a generator. 

209. Can the direction of rotation of arma¬ 
ture be determined from the position of the 
third brush? 

210. If the battery is disconnected from the 
generator, will the generator have regulation? 

211. If a car is to be run without the 
battery, what precaution should be taken? 

212. Must a generator having field distor¬ 
tion regulation or a vibrator regulator have 
series field coils? 

213. Can the shunt field of a generator be 
tested with a buzzer? 

214. Can the series field coils of a starting 
motor be tested with a buzzer? 

215. In what ways do starting motors differ 
from the generators? 

216. Explain how to test for (a) open field 
coils; (b) shorted field coils; (c) grounded 
field coils. 

217. What effect do partially shorted field 
colls have on starting motors? On genera¬ 
tors? 

218. Explain how an armature may be 
tested for (a) shorted coils; (b) open armature 
coils; (c) grounded armature coils. 

2lk Explain why a Ford horn will not op¬ 
erate on a direct current. 

220. What are the adjustments on a motor 
horn ? 

221. Describe three ways of dimming the 
headlights. 






330 


ADVANCED ELECTRICITY 



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ADVANCED ELECTRICITY 


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WIRING DIAGRAMS 


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337 




WIRING DIAGRAMS 



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338 


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339 



COLE MODEL 8-70 m SERIRLSIOOIJOSAOOO DELCO SYSTEM 












































































































340 


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342 


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345 



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346 


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347 




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352 


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353 













































































































































































































354 


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358 


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360 


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INDEX 


A 

Ammeter— 

Magnetic Vane. 318 

Movable Coil. 317 

Plunger Type. 316 

Ampere . 210 

Ampere Capacity. 216 

Ampere Hour Capacity. 216 

Ampere Turns. 227 

Anti-Freezing Solutions. 67 

Armatures— 

Drum Wound. 283 

Ring Wound.-t. 281 

Lap Wound. 284 

Wave Wound., . .. 284 

Armature Reaction— 

Generator . 287 

Motor . 289 

Armature Testing. 323 

Bar to Bar. 325 

Open Circuits. 325 

Short Circuits. 325 

Automatic Spark Advance. 244 

B 

Battery Indicator. 318 

Bearings .121-123 

Annular Ball. 122 

Babbitt . 121 

Ball Thrust. 124 

Bronze . 121 

Cup and Cone. 122 

Plain Roller. 122 

Plain Thrust..... 124 

Tapered Roller. '.....• . 122 

Bendix Drive. 299 

Bolts and Nuts. 117 

Bore, (definition) . 8 

Brakes . 186 

Controls . 187 

Engine as a brake. 187 

Troubles . 188 

Breakers— 

Open Circuit Type. 241 

Closed Circuit Type. 241 

Adjustment of Points. 242 

c 

Calorific Value. 1^ 

Camber of Front Wheels. 125 


Cams . 36 

Camshaft . 36 

Methods of Driving. 35 

Timing—Two-cylinder. 44 

Four-cylinder . 47-48 

Six-cylinder . 50-51 

Eight-cylinder . 53 

Twelve-cylinder. 55-57 

Carbon Deposit— 

Causes, Effect and Removal. 13 

Carburetion, Principles. 85 

Carburetors . 85 

Ball and Ball. 94 

Marvel . 89 

Rayfield . 92 

Schebler . 93 

Stromberg . 90 

Zenith . 87 

Caster Effect of Front Wheels. 125 

Charging Circuit. 300 

Charging Rate. 223 

Chassis . 121 

Circular Mil. 213 

Circular Mil Foot. 213 

Clearance, (volumetric). 8 

Clutches . 141 

Cone . 141 

Disc . 144 

Disc, Dry. 145 

Disc, Lubricated. 144 

Plate . 145 

Clutch Brake . 145 

Clutch Troubles. 152 

Dragging . 154 

Grabbing . 152 

Slipping . 152 

Spinning . 152 

Stuttering . 154 

Combustion . 1 

Combustion Chamber. 8 

Combustion Temperature. 7 

Commutation Points— 

Generator . 287 

Motor . 289 

Commutator and Brushes— 

Care of. 311 

Compression— 

Object . 4 

Effect . 7 

Pressures . 7 

Condenser . 233 


























































































372 


INDEX 


• Conductors . 

Connecting Rod— 

Alignment . 

Fitting Bearings. 

Material and Construction. 

Purpose . 

Control Levers, Gas and Spark. 

Cooling Systems— 

Air Cooling. 

Water Cooling. 

' Circulating. 

Thermo-Syphon . 

Copper Wire, Sizes and Capacities. 

Counter E. M. F. 

Crankcase . 

Crankshaft . 

Alignment . 

Clearance . 

Counterbalance . 

Fitting Bearings. 

Material and Construction. 

Pouring Bearings. 

Repairing . 

Types—Two-cylinder. 

Four-cylinder . 

Six-cylinder. 

Eight-cylinder “V”. 

Eight-cylinder vertical.. . . 

Twelve-cylinder “V”. 

Cut-Out Relay— 

Adjustments, Operation and Tests. 

Cycle. 

Cycle of Operations— 

Four Stroke Cycle Engine. 

Two Stroke Cycle Engine. 

Cylinders— 

Finishing . 

Material and Construction. 

Multiple Cylinder Construction. . . 

Troubles and Repairs. 

Types . 

D 

Density . 

Differential . 

Displacement . 

Distributor . 

Drills .,. 

Dry Cell. 

Dynamic Balance. 

E 

Eccentric Shaft., 

Timing . 

Electric Battery. 

Electric Cell. 


Electric Circuits.208-210 

Parallel . 211 

Series . 211 

Electric Horn— 

Ford .314-315 

Motor Driven. 316 

Vibrating . 314 

Electric Power. 212 

Electromagnet .‘. 228 

Polarity . 229 

Strength . 229 

Electromagnetic Induction. 229 

Electromagnetic Starting Motor Con¬ 
nection . 299 

Electromagnetism . 225 

Electromotive Force (E. M. F.). 208 

Elementary Electricity. 207 

Engine Starting Devices. 96-292 

Expansion Principle, Internal Combus¬ 
tion Engine . 4 

F 

Farad . 233 

Field Distortion— 

Generator . 287 

Motor . 289 

Field Windings. 285 

Final Drive, Bevel. 174 

Worm Drive. 183 

Firing Orders— 

Four-cylinder . 47 

Six-cylinder . 49 

Eight-cylinder “V”. 51 

Eight-cylinder Vertical. ... 54 

Twelve-cylinder “V”. 55 

Firing Point. 41 

Flame Propagation . 10 

Flexible Coupling. 169 

Flywheel . 40 

Markings . 42-43 

Four Stroke Cycle Principle. 3 

Front Axles— 

Alignment . 125 

Mounting . 125 

Types. 124 

Front Wheel Mounting. *131 

Fuelizer, Packard. 91 

Fuel Systems. 79 

. Gravity . 79 

Pressure . 79 

Vacuum . 80 

o 

Gaskets . 88 

“Gather” of Front Wheels. 128 

Gear Shifts . 159 

Magnetic . 320 


208 

21 

19 

17 

3 

141 

61 

63 

63 

63 

213 

290 

61 

23 

24 

26 

23 

25 

23 

25 

23 

44 

47 

48 

51 

54 

55 

300 

1 

3-4 

96 

12 

11 

41 

12 

10 

10 

169 

8 

241 

115 

215 

23 

36 

60 

216 

213 































































































INDEX 


373 


Gear Shift, Interlocking Device. 161 

Generators— 

Principles—Alternating Current.. . 280 

Direct Current. 281 

Windings, Compound.286-301 

Series.286-289 

Shunt. 286 

Generator Output Regulation. - 302 

Regulators— 

Reverse-Series Field Coils. 303 

Vibrator, Current Type. 306 

Current Voltage Type. . . 309 

Voltage Type. 306 

Field Distortion Regulation. 309 

H 

Headlight— 

Dimming . 322 

Focusing . 322 

Reflectors . 323 

Horn— 

Ford .314-315 

Motor Driven. 316 

Vibrating . 314 

Horsepower . 9 

S. A. E. Formula. 9 

Hydrometer . 218 

1 

Ignition. 95-235 

Ford System. 266 

High Tension, “Jump Spark”. 235 

Low Tension, “Make and Break”. . 235 

Ignition Resistance. 242 

Ignition Switch, Automatic. 320 

Ignition Timing. 269 

Induced E. M. F. 229 

Induction—Mutual . 231 

Self. 230 

Induction Coil. 232 

Insulators . 208 

Internal Combustion Engines— 

History . 1 

Description . 3 

IR Drop. 211 

K 

Knight Sleeve Valve Engine. 57 


L 


Lubricating Systems— 

Force Feed. 74 

Force Feed and Splash. 73 

Full Force Feed. 75 

Splash . 71 

Splash Circulating. 72 

M 

Magnetic Circuits— 

Generators and Motors. 285 

Magnetic Field— 

Around Conductor. 225 

Around Parallel Conductors. 226 

In Coil. 227 

Magnetic Gear Shift. 320 

Magnetic Lines of Force. 203 

Magnetism . 203 

Magnetos . 248 

Direction of Rotation. 252 

“Dixie” . 257 

Ford . 263 

High Tension Dual. 261 

High Tension Duplex. 260 

High Tension (revolving arma¬ 
ture) . 256 

Inductor Type . 257 

“K-W” . 259 

Low Tension Dual. 254 

Low Tension (revolving armature) 250 

Principles . 248 

“Teagle” . 260 

Voltage and Current Curves. 249 

Manifolds— 

Inlet . 39 

Exhaust. 39 

Water . 66 

Micrometer Caliper. 118 

Molecular Theory of Magnets. 205 

Motors— 

Armature Reaction, Field Distortion 289 
Operation—Compound, Series and 

Shunt . 291 

Output . 290 

Points of Commutation. 289 

Principles .287-288 

Torque . 290 

Motor-Generator . 291 

Muffler . 190 

Mutual Induction. 231 


Lamp Bulbs. 321 

Lamp Sockets. 321 

Lighting . 321 

Losses in Internal Combustion Engine. 7 

Lubrication . 67 


N 

Negative Charge. 208 

Neutral Point— 

Generator . 287 

Motor . 289-290 


















































































374 


INDEX 


o 

Ohm . 

Ohm’s Law. 

Oil Gauge or Indicator. 

Oil Pan. 

Oil Pump— 

Gear . 

Plunger . 

Overrunning Clutch. 

P 

Permeability . 

Piston— 

Clearance, Material, Construction 

and Types. 

Piston Pin. 

Piston Ring. 

Clearance, Pitting. 

Piston Speed. 

Pivot Bolt. 

Polarity Ignition Switch. 

Polarity of Coils. 

Polarization of Cells. 

Poles of Magnets. 

Positive Charge. 

Power ... 

Power Charts— 

Single-cylinder . 

Two-cylinder . 

Four-cylinder . 

Six-cylinder. 

Eight-cylinder. 

Twelve-cylinder . 

Pre-ignition . 

Pressure, (definition). 

Compression . 

Prony Brake. 

Propeller Shaft. 

R 

Radiators . 

Reamers .•.. 

Rear Axles. 

Plain Live. 

Semi Floating. 

Three-Quarter Floating. 

Full Floating. 

Worm Drive. 

Rear Axle Housing. 

Recharging Magnets. 

Reluctance . 

Residual Magnetism. 

Resistance . 

Retentivity. 


Reverse-Series Field Regulation....... 303 

Rocker Arms. 29 

S 

Scavenging . 10 

Self Induction. 230 

Slip Joint. 168 

Spark Advance and Retard. 243 

Spark Plugs. 60-247 

Gap Adjustment. 243 

Specific Gravity— 

Definition . 10 

Electrolyte. 217 

Sulphuric Acid. 218 

Specific Heat. 10 

Springs .188-189 

Starting Motors— 

Characteristics . 291 

Connections to Battery. 292 

Connections to Engine. 292 

Bendix Drive. 299 

Electromagnetic . 299 

Overrunning Clutch. 294 

Sliding Gears.294-296 

Static Balance. 23 

Steering Devices. 132 

Planetary . 137 

Split Nut. 134 

Worm, Screw and Nut. 137 

Worm and Nut. 135 

Worm and Sector. 134 

Worm and Wheel.:. 133 

Steering Knuckle. 125 

Steering Knuckle Arms. 127 

Storage Batteries. 217 

Ampere Hour Capacity. 219 

Charging Circuit Diagram. 221 

Charging Rate. 223 

Chemical Action—Charge. 221 

Discharge. 219 

Electrolyte . 217 

Freezing Temperatures. 224 

Jars . 217 

Plates . 217 

Polarity Test. 222 

Separators . 218 

Specific Gravity of Electrolyte.... 217 

Storing of Batteries. 225 

Storage of Car. 192 

Stroke, (definition). 8 

Summaries— 

Engine . 100 

Chassis . 193 

Elements of Electricity. 271 

Advanced Electricity. 326 


210 

210 

75 

61 

78 

75-77 

294 

205 

14 

16 

15 

16 

8 

125 

241 

227 

214 

203 

20S 

9 

45 

45 

47 

49 

51 

55 

10-13 

8 

7 

291 

169 

66 

115 

171 

173 

173 

174 

174 

183 

180 

206 

206 

286 

212 

205 




































































































T 


Tables— 

Anti Freezing Solutions. 67 

Bolts and Nuts. 117 

Camber and Gather. 193 

Compression Temperatures. 7 

Engine Losses. 7 

Flat Wrenches. 120 

Standard Copper Wire. 213 

Tappets . 29 

Test Lamp and Buzzer. 313 

Thermal Efficiency. 7 

Throttle Valve. 88 

Tires . 191 

“Toe In” of Front Wheels. . ;. 128 

Tools . 115 

Chisels and Drifts. 116 

Hammers. 116 

Reamer . 115 

Screw Driver. 115 

Twist Drills. 115 

Torque— 

Definition .. 10 

Arms and Rods. 169 

Transmissions . 154 

Planetary . 163 

Planetary Adjustments. 166 

Progressive . 154 

Selective . 157 

Transmission Gear Lock. 161 

Twist Drills. 115 

Two Stroke Cycle Engine. 96 

u 

Universal Joint. 168 

V 

Vacuum Tank.80-81-84 

Valves— 

Clearance . 27 

Grinding . 27 

Material and Construction. 26 

Opening and Closing, Exhaust.... 38 

Inlet. 37 

Troubles and Repairs. 26 

Types . 26 

Valve Cage. ,32 

Valve Chamber.‘ 40 

Valve Springs. 29 

Valve Spring Compartment. 35 

Valve Timing. 40 

Velocity— 

Angular or Circular. 8 

Linear . 8 

Vibrating Coil. 267 

Volt . 210 


Voltage Drop. 211 

Voltage Regulation— 

Reverse-Series Field. 303 

Third Brush, Field Distortion..... 309 

Vibrator, Current Type. 306 

Vibrator, Current Voltage Type. . . 309 . 

Vibrator, Voltage Type. 306 


w 


Water Manifold. 66 

Water Pumps. 66 

Watt . 212 

Wire Gauges. .. 213 

Work, (definition). 8 

Worm Drive Rear Axle. 183 

Wrenches . 120 

Wiring Diagrams: 

Allen. 332 

Anderson . 332 

Apperson . 334 

Auburn . 333 

Buick-4 . 335 

Buick-6 . 335 

Briscoe . 334 

Cadillac . 336 

Case .;. 336 

Chalmers . 337 

Chandler . 337 

Chevrolet . 338 

Cleveland . 338 

Cole . 339 

Columbia . 339 

Cunningham . 340 

Dixie Flyer . 340 

Dodge . 341 

Dorris . 342 

Dort . •.. 342 

Elcar . 343 

Elgin . 343 

Elk-Hart . 344 

Essex . 345 

Ford . 344 

Franklin . 346 

Haynes . 346 

H. C. S. 347 

Holmes . 347 

Hudson . 348 

Hupmobile . 348 

Jordan . 349 

King . 349 

Lafayette . 350 

Lexington . 350 

Liberty . 351 

Lincoln . 351 

Locomobile. 352 

Marmon . 353 

Maxwell . 352-353 

Mercer . 354 

Mitchell . 354 











































































































376 


INDEX 


Wiring Diagrams—Continued 

Monroe . 355 

Moon . 355 

Nash . 356 

National . 356 

Oakland . 357 

Oldsmobile . 357 

Packard Single-6 . 358 

Packard Twin-6 . 358 

Paige . 359 

Paterson . 360 

Peerless . 360 

Pierce Arrow . 361 

Premier . 361 

Reo . 362 

R. & V. Knight. 362 


Saxon . 363 

Scripps-Booth . 363 

Standard. 364 

Stanley . 364 

Stearns . 365 

Stephens .■.. . 365 

Studebaker (Big Six and Special) 366 

Studebaker (Light Six, Remy). .. 366 

Studebaker (Light Six, Wagner). 367 

Stutz . 367 

Templar . 368 

Velie . 368 

Westcott . 369 

Wills St. Claire. 369 

Willys Knight . 370 

Winton . 370 










































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